1.
underwear, undershirt, undergarments
Clothing worn directly against the skin, under other clothes. Typically refers to undershirts, tank tops, or similar garments.
肌着 literally means 'skin clothes': garments worn directly against the 肌 (skin). It is the usual word for babies' undershirts and for cotton undershirts worn to absorb sweat.
Similar words
- 下着: underwear (the general word, including underpants and bras)
- インナー: inner wear (loanword, common in shops)
Watch out
In everyday use 肌着 mostly means a top worn under a shirt; for underpants people say パンツ or 下着.