To moan means to make a long, low sound that expresses pain, sadness, or discomfort. When someone stubs their toe hard, they might moan from the sharp ache. A person with a bad stomachache might lie in bed moaning softly. The sound is different from a scream or a shout: it's deeper, longer, and comes from deep in the throat.

People also moan to express complaints or unhappiness about something. If your class has to stay inside for recess because of rain, you might hear students moaning about the unfairness. When someone constantly complains, we sometimes say they're moaning and groaning about everything.

The wind can moan too. On a stormy night, wind blowing through trees or around the corners of a house creates an eerie moaning sound that can be both haunting and beautiful. Old ships at sea were said to moan and creak as they rocked in the waves.

A moan (as a noun) is the sound itself: “We heard a moan coming from the next room.” Whether from physical pain, disappointment, or even the weather, a moan is that distinctive low, drawn-out sound that expresses something unpleasant.