Green’s Dictionary of Slang

1. (US campus) one who is good at seducing others.

1963		Mad mag. Jan. 31: The one sitting in the front on the right (who is usually the best ‘make-out’) [...] leans out as they pass females, and shouts clever, daring pick-up phrases .
1972		B. Hannah Geronimo Rex 111: She told me she was a make-out in Holly Springs and ahd been the cause of a lot breaking up among couples [Simes:DLSS].

2. (US, also making-out) romantic and sexual behaviour; often attrib., e.g. make-out session.

1964		‘R. Blake’ Amer. Dict. Sexual Terms 127: makeout (sl) Success with a girl in the sexual sense; copulation; intercourse with any love partner.
1970		Meyer & Ebert Beyond Valley of the Dolls [film script] Am I interrupting something? [...] Only a little make-out session .
1972		E. Grogan Ringolevio 86: Walking with chicks for a Sunday stroll and make-out in the park.
1978		R. De Christoforo Grease 182: We went into a heavy, juicy make-out.
1985		‘Thommo’ Dict. Aus. Swearing & Sex Sayings 82: MAKE OUT — A passionate, emotional, romantic and tender fuck, or a frivolous attempt at intercourse by a juvenile.
1999		Guardian G2 24 June 2: We had a sort of making-out session.
1999		Indep. Rev. 18 July 12: From the age of 14, she went to ‘make-out parties’, where ‘you invited a group of boys and girls, and you turned out the lights, and you played ... games.’.
2005		Mad mag. Nov. 20: After a really steamy make-out session, don’t ask her to give you extra credit.
2012		M. Lacher On the Bro’d 227: ‘I got some make-out action from my hottie’.
2023		(con. 1962) J. Ellroy Enchanters 73: The big new thing? It’s the prearranged makeout date.