Underarm refers to the area under your arm where your upper arm meets your body, also called the armpit. This spot stays warm and hidden most of the time, which is why people often apply deodorant there to stay fresh. Doctors sometimes check your underarm area during medical exams because it contains lymph nodes that help your immune system fight infections.

The word also describes a specific way of throwing. When you throw something underarm, your hand starts low and swings upward in an arc, like gently tossing a ball to a young child or rolling a bowling ball. This differs from an overhand throw, where your arm comes from above your shoulder. An underarm throw gives you more control and a gentler delivery, which is why it's useful when you want to toss something carefully to someone or when rules require it.

You might also see underarm used to describe clothing, like the underarm seams of a shirt where the sleeves attach to the body.