Prepper glossary: bug out, EDC, gray man and more

ABC extinguisher: Dry-chemical extinguisher rated for ordinary combustibles (A), flammable liquids (B) and electrical fires (C): almost anything that can burn in a home.
BMS: Protection circuit inside lithium batteries: it cuts charging or discharging before the battery is damaged or overheats. Look for batteries that include one.
Bug in: Staying home during an emergency and living off your household supplies. It's the safest option in most situations: outages, storms, heat waves. See the 72-hour kit.
Bug out: Leaving home because staying is more dangerous, for example due to a wildfire or flood, or because authorities order an evacuation.
Bug out bag go-bag: A pre-packed bag with what you need for about 72 hours away from home. Also called a go-bag or 72-hour bag. See the 72-hour bag.
Carbon monoxide CO: An odorless, colorless gas produced by grills, charcoal, generators and combustion heaters. In an enclosed space it poisons without warning: that's why they're never used indoors.
CPR: Cardiopulmonary resuscitation: hard compressions in the center of the chest when someone isn't breathing. It keeps blood reaching the brain until help arrives. You can learn it in a one-day course.
Cryptosporidium: A parasite in contaminated water that resists chlorine: some tablets need hours to kill it. Boiling or filtering does remove it.
DANA cut-off low: Spanish acronym for an isolated upper-level low: a pocket of cold air aloft that can dump torrential rain in a few hours, as in Valencia in 2024.
EDC everyday carry: What you carry every day: phone, keys, a small flashlight, cash, medication. See car and everyday carry.
Emergency alerts EU-Alert, WEA: Official alerts sent to every phone in an area: the phone sounds even on silent when there's a serious emergency nearby. In the US they're Wireless Emergency Alerts; in Europe, EU-Alert.
Emergency fund: Savings set aside for the unexpected, usually three to six months of basic expenses. Many experts see it as the most important prep after water and food.
FIFO first in, first out: The method for rotating your pantry: use the oldest items first.
Filter vs. purifier: A water filter removes bacteria and parasites; a purifier also removes viruses. Most portable filters don't remove viruses. See water.
FRS and PMR446: License-free walkie-talkies: FRS in the US and Canada, PMR446 in Europe. See the family plan.
Get-home bag: A small bag kept at work or in the car so you can walk home if transport fails.
Gray man: Blending in: normal clothes and a civilian-looking bag instead of tactical gear. It lowers the risk of theft and conflict during evacuations.
HDPE: High-density polyethylene: the plastic with number 2 in the recycling triangle. It's tough, doesn't leach into water and is the one recommended for storing it.
Heat stroke: The body's temperature control fails: hot, dry skin, confusion or fainting. It's a medical emergency: call for help and cool the person down.
Hypothermia: A dangerous drop in body temperature. It doesn't need to freeze: being wet, still and in the wind is enough.
IFAK individual first aid kit: A personal first aid kit focused on severe bleeding. See the first aid kit.
LiFePO4 lithium iron phosphate: A type of lithium battery safer than the one in your phone: it's very hard to set on fire and lasts thousands of charge cycles. The one to choose for a power station.
LoRa: A radio technology for sending small amounts of data very far on very little battery. It's what Meshtastic runs on. See Meshtastic.
Meshtastic: An open-source project that builds a messaging network with LoRa radios, with no internet, no license and no fees. See Meshtastic.
MPPT charge controller: A controller between the solar panel and the battery that charges it without damage. MPPT gets more energy out of the panel than the cheaper PWM type.
Mylar: Aluminum-and-plastic bags that block light, moisture and air, used for long-term dry food storage.
N95 FFP2: A mask that filters at least 95% of particles. It protects against wildfire smoke and dust after a collapse; surgical masks don't.
Normalcy bias: The tendency to believe what's happening isn't serious and things will soon be back to normal. It delays decisions. See mindset.
OPSEC operational security: Not telling everyone, or posting online, what you have stored. Part of the gray man idea.
Oral rehydration solution ORS: Water with sugar and salt, or pharmacy sachets, that replaces what diarrhea or vomiting takes out. It prevents dehydration, which is what makes diarrhea dangerous.
Oxygen absorber: A small packet of iron powder that removes oxygen from a sealed container. With mylar bags, it lets rice or beans keep for decades. See long term.
PACE plan: A communication plan with four levels: Primary, Alternate, Contingency and Emergency. If one fails, everyone knows the next one without having to discuss it. See self-reliance blueprint.
PLB personal locator beacon: A device that sends a distress signal via satellite to search and rescue, with no subscription. See PLBs.
Power station: A large battery with outlets and USB ports that's safe indoors and can be recharged with a solar panel. See power stations.
Prepping: Preparing in advance for emergencies and crises: supplies, skills and plans so your family is OK without depending on immediate help. A person who does it is a prepper.
Pure sine wave inverter: A device that turns a 12 V battery's current into household current. A pure sine wave inverter is safe for sensitive devices; cheaper ones may damage them.
Retained-heat cooking: Bringing a pot to a boil for a few minutes, then putting it, lid on, into an insulated box to finish cooking on its own. It saves about half the fuel. See cooking without power.
Rotating pantry: A food supply that's continuously eaten and restocked, oldest first. No waste, and everything stays in date. See pantry.
Rule of threes: A rough order of priorities: about 3 minutes without air, 3 hours without shelter in harsh conditions, 3 days without water and 3 weeks without food. It helps decide what to prepare first; it isn't an exact figure.
Shortwave SW: A radio band that reaches thousands of miles by bouncing off the atmosphere. Useful for news from other regions if local stations go down.
SHTF: An acronym common on forums for a serious crisis. On this site we prefer to talk about specific, likely emergencies.
Sodium hypochlorite: The chemical name for bleach. Unscented and without detergent, a few drops disinfect drinking water. See water.
Tourniquet: A band tightened above a severe wound on an arm or leg to stop the bleeding. It saves lives, but you need to learn how to apply it in a course.
Two is one, one is none: A prepper saying: if you have only one way to do something critical, like purifying water or making light, expect it to fail. Always have a backup.
UPS: Uninterruptible power supply: a battery that kicks in instantly, with no gap, when the power goes out. Useful for the router or a medical device.
Wh and mAh: Units for battery capacity. Watt-hours (Wh) let you compare different batteries; mAh depends on voltage and tends to inflate the real figure on power banks.