/ ˈsɪŋglət; NAmE / noun
( BrE ) a piece of clothing without sleeves, worn under or instead of a shirt; a similar piece of clothing worn by runners, etc.
—compare vest
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WORD ORIGIN
mid 18th cent. (originally denoting a man's short jacket): from single (because the garment was unlined) + -et , on the pattern of doublet .