(Of women's clothing) designed or tailored in a masculine style; specifically (of briefs, bikini bottoms, etc.) cut straight and low across the upper thigh to resemble snugly-fitting shorts.
Origin
1950s; earliest use found in The New York Times.
Definition of boy-cut in US English:
boy-cut
(also boy's cut, boys' cut)
adjective
US
(Of women's clothing) designed or tailored in a masculine style; specifically (of briefs, bikini bottoms, etc.) cut straight and low across the upper thigh to resemble snugly-fitting shorts.