Definition of trap

i. Any dark-colored fine-grained nongranitic rock, such as a basalt, peridotite, diabase, or fine-grained gabbro; also applied to any such rock used as crushed stone.

Synonym of: trapp, trap rock, trappide.

Compare with: whinstone.

Ref: AGI

ii. A device for separating suspended sediment from flowing water; e.g., a sand trap.

Ref: AGI

iii. A door used for cutting off a ventilating current and that is occasionally opened for haulage or passage.

See Also: trapdoor

Ref: Fay

iv. A device to separate denser material from less-dense material, such as entrained water in a stream or a compressed-air line.

Ref: Long

v. That portion of any mass of porous, permeable rock that is sealed on top and down the sides by relatively nonporous and impermeable rock and that lies above the intersection of a horizontal plane passing through the lowest point of complete sealing.