armpit hair
armpit sweat
under the armpit
A: Why are you wearing a sweater in this heat?
A：这么热的天你为什么要穿毛衣？
B: I spilled some sweat on my armpit.
B：我把汗洒到腋下了。
1) 腋窝
2) 腋下的部位
1. 腋窝
noun
1. The hollow area under the arm where the arm joins the body.
Synonym: axilla