Reported by Mark Mandel on ADS-L yesterday, ace for asexual ‘person who feels no sexual attraction to others’ (independent of feeling romantic interest) — a clipping of the base word, making the term roughly comparable in form to the clippings bi for bisexual, homo for homosexual, and hetero for heterosexual (though these items are not fully comparable in tone or style). Ace stands out because, unlike the others, it’s not a prefix on its own, but rather a prefix (a-) plus the following consonant.
OED2 on asexual has been unrevised for nearly a century and has only the use in biology for ‘not sexual, without sex’ and more generally, for ‘without sexuality’, with cites from 1896 (the “asexual existence” in monastic contexts), 1903 (“women are more asexual than men”, meaning that men are more sexual than women), and 1928 (D.H. Lawrence, “their false sex and hypocrisy” … “their asexual sexuality”).
Urban Dictionary has the clipping, in this entry:
Asexual to any degree. Using “ace” for “asexual” gained popularity on AVEN (www.asexuality.org) and has inspired the use of the spade as a symbol of the asexual community. (Cheerio_Koroke 12/24/08)
(a little joke on ace of spades, apparently). Like the other sexual clippings and their bases, this one can be used as either adjective (“I’m ace”) or noun (“I’m an ace”).
The cites seem to all be pretty recent, but within the relevant community the word seems to be taken for granted. Here’s a passage Mandel found where it’s used without explanation in the event name Carnival of Aces:
an asexual ya [Young Adult] heroine? why not? by R.J. Anderson 11/27/12
Later in this piece:
On the other hand, I also didn’t want to fall into the trap of treating asexuality in a careless, superficial way, or allowing the non-ace reader to mistake it for a symptom of Tori’s abnormal biology (a key plot point of the story). So I spent a lot of time reading ace blogs and Tumblrs to find out what cliches and myths about asexuals to avoid and if possible, to directly address and counter them.