A trap is a device intended to cause harm, capture, detect, or inconvenience an intruder.

• Trapping - traps designed to capture or kill an animal
• Booby trap - designed as an antipersonnel device that can also be employed against civilians
• In role-playing games, traps may be randomly scattered as obstacles in dungeons.
• In programming, a trap can refer to code designed to capture errors and reveal where they are.
• In networking a bot trap is a script designed to identify and block bots that disobey the restrictions on a server.
• In geology, a trap is a rock formation in which water, salt or hydrocarbons may collect
• In plumbing, a trap is a U shaped pipe located below a drain. The bend in the pipe reserves a small amount of water, preventing the escape of sewer gases.
• a trap can also be a statement or question phrased in such a way that any valid answer or reply would imply something the responder does not intend.
• In computing, a trap is a processor exception.
• In shooting, trap is an activity similar to skeet which involves shooting clay pigeons - the device which launches the clays is also referred to as a "trap".
• In Horseriding, a "trap" refers to the device which attaches a carriage to a pony.

Generally, a device which detects an intruder, or is designed to inconvenience or restrict an intruder may also be referred to as a "trap".