Torpor is a state of mental or physical sluggishness and inactivity. When you're in torpor, you feel slow, dull, and unable to think clearly or move energetically. Imagine how you might feel on a sweltering summer afternoon: too hot and drowsy to do anything but lie on the couch in a daze. That heavy, sleepy feeling is torpor.

The word often describes the sluggishness that comes from extreme heat, boredom, or exhaustion. A classroom might fall into torpor during the last hour of a long school day, with students barely able to keep their eyes open. A town might sink into torpor during the hottest part of summer, when even the dogs lie motionless in the shade.

In biology, torpor has a specific meaning: it's when animals deliberately slow down their body functions to conserve energy, similar to hibernation but usually shorter. Hummingbirds enter torpor at night, lowering their heart rate and body temperature dramatically to save energy until morning.

The word suggests something deeper than ordinary tiredness. You might be tired after playing soccer, but torpor is that foggy, heavy feeling where you can barely muster the energy to think or care about anything.