UNDERSHIRT Meaning of UNDERSHIRT in English un ‧ der ‧ shirt /ˈʌndəʃɜːt $ ˈʌndərʃɜːrt/ BrE AmE noun [countable]American English a piece of underwear with or without arms, worn under a shirt Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012