1. n. 
A configuration of rocks suitable for containing hydrocarbons and sealed by a relatively impermeable formation through which hydrocarbons will not migrate. Traps are described as structural traps (in deformed strata such as folds and faults) or stratigraphic traps (in areas where rock types change, such as unconformities, pinch-outs and reefs). A trap is an essential component of a petroleum system.
See: anticlinal trap, anticline, channel, closure, closure, critical moment, diapir, evaporite, fault trap, field, flower structure, formation, halite, impermeable, migration, oil field, oil pool, petroleum system, pinch-out, primary migration, prospect, salt dome, seal, shale, spill point, stratigraphic trap, structural trap, structure, subsalt, syncline, unconformity trap