Your armpit is that little nook or dip right under your shoulder where your arm meets your side. Sometimes, especially after playing hard or on a hot day, armpits can get a little sweaty. That's because our bodies have a way of cooling us down, and sweat helps with that.

Example

1. Open your armpit, so I can take your temperature.
2. He tucked the gun under his armpit.
3. Spicy food caused a burning armpit tingle.