undershirt
/ˈʌndərʃɜːrt/
noun
- A piece of clothing worn under a shirt, usually next to the skin, to absorb sweat or provide warmth.
- He put on a clean undershirt before buttoning his dress shirt.
- The athlete changed his undershirt after the game because it was soaked with sweat.
- In winter, she wears a thermal undershirt to stay warm under her sweater.