Green’s Dictionary of Slang

a heterosexual.

1972		B. Rodgers Queens’ Vernacular.
1999		Indep. on Sun. Culture 15 Aug. 2: That kind of cheeky het’s camp that hugely confident people [...] do so well.
2000		Observer 31 Dec. 30: Setting yourself up to inflame the ‘breeders’, or ‘hets’, is only the flipside of craving approval.
2019		P. Baker Fabulosa 293/2: hettie heterosexual.