Green’s Dictionary of Slang

1. (N.Z.) a married woman’s lover.

1948

D. Ballantyne Cunninghams (1986) 125: Come off it. You wouldn’t like your sister-in-law to park her ears to all I know about you. You and your bow-tie.

2. (US) a lesbian; usu. attrib.; thus bow-tie club, bow-tie party.

1953

W. Brown Monkey On My Back (1954) 199: The tourist, too, may wander into fag joints and bow tie clubs. [Ibid.] 203: ‘There’s a party going on – a hairpin joint.’ ‘A what?’ ‘Hairpin joint – bow tie party – lesbians.’.