undershirt
Clothes
un·der·shirt /ˈʌndəʃɜːt $ ˈʌndərʃɜːrt/ noun [countableC] 
DCC American EnglishAmE a piece of underwear with or without arms, worn under a shirt 汗衫；背心 →5 see picture at 见图 underwearExamples from the Corpus
undershirt• High above she saw Mr Yeltsin in an undershirt, muscles bulging, and a mischievous grin on his sweaty face.• She pulled on her underpants and then an undershirt.• Coming into the door, he took off his shirt and undershirt and began hugging the absolute stranger, Mary Bettencourt.• He had his undershirt off now.• A man sitting in his undershirt, drinking coffee, said yes, they had a bed.• His white linen undershirt was open at the throat, drawing Isabel's gaze upward.• With his left hand he tore open the tunic of his uniform and drew up the undershirt, baring the flesh.