sexual preference

   homosexuality

   Not in the literal sense referring to gentlemen who prefer blondes or ladies who favour moustaches. Also as sexual irregularity, orientation, proclivity, or tropism:

    ... impossible to ask questions about (as they said on the current affairs programmes) Ron's 'sexual preference'. (Keneally, 1985)

    She spoke of your sexual irregularities. (Burgess, 1980)

    But my sexual orientation was the true instigator of apostasy, (ibid.)

    She discovered her boyfriend's, uh, sexual proclivities. (Sanders, 1986)

    ... it is replacing your former militancy on behalf of the sexual tropism you and I both represent. (Burgess, 1980 — tropism is normally a vegetable rather than an animal response to a stimulus, but the Greek source meant a turn)

   To be sexually non-conformist is to be homosexual or bisexual:

    His collaboration with the leading sexologist Wilhelm Reich... stood him in good stead when dealing with the sexually non-conformist Five from Cambridge. {Daily Telegraph, 5 April 1998, writing of their Russian controller, Arnold Deutsch and the homosexual British spies — Blunt, Philby, McLean, Burgess, and Cairncross)

   Sexual variety usually means no more than promiscuity.