UNDERSHIRT
singlet, vest, undershirt
(noun) a collarless men’s undergarment for the upper part of the body
Source: WordNet® 3.1
Etymology
Noun
undershirt (plural undershirts)
(fashion) An undergarment worn beneath a shirt, often collarless and sleeveless.
Usage notes
As a rather generic term, undershirt is more often used in reference to male clothing, while female equivalents employ more specialized terminology.
Synonyms
• singlet, wife-beater (men); vest (UK); see also underbodice (female equivalents)
Source: Wiktionary
Un"der*shirt`, n.
Definition: A shirt worn next the skin, under another shirt; -- called also
undervest.
Source: Webster’s Unabridged Dictionary 1913 Edition