Pent (usually seen as pent-up) describes feelings or energy that have been held inside or trapped for so long that they're building pressure, like water behind a dam.

When you've been sitting still through hours of classes and can't wait for recess, that restless feeling is pent-up energy. When someone has been holding back anger or frustration for days and finally explodes over something small, those were pent-up emotions. A dog that's been inside all day has pent-up energy that bursts out the moment you open the door.

Think of how animals pace restlessly when confined, or how steam builds pressure inside a covered pot. That sense of something contained and building intensity is what pent captures.

You might hear about pent-up demand (when people have been waiting to buy something for so long that sales explode when it becomes available) or pent-up creativity (when an artist finally gets to work after being too busy with other things). The pent-up part always suggests that release is coming, or desperately needed. Whatever's been held back won't stay contained forever.