An armpit is the hollow area under your arm where your shoulder connects to your body. If you raise your arm straight up and look at the spot where your arm meets your torso, that's your armpit.

Armpits are one of the warmest spots on your body, which is why they tend to sweat more than other areas, especially when you're nervous, hot, or exercising. This is also why people use deodorant there. The scientific name for your armpit is the axilla, but almost everyone just says armpit in everyday conversation.

The word appears in some common expressions too. When someone calls a place “the armpit of America” or says a town is “an armpit,” they mean it's the worst or least pleasant place around. This usage is rude and unkind, comparing the place to a body part that people associate with sweat and odor. You might also hear someone say they have something “up to their armpits,” meaning they're completely overwhelmed or buried in work, like being in water so deep it reaches your armpits.