The summary: 40-mutter crankypants smartass freakazoid fairly-oddparent seeks same...or different. Surprise me. Clown suit optional.
The standard adjectives: Happily freaky, but capable of looking respectable when necessary. Polysyllabic, but I like my dumb pleasures too. In decent shape, but certainly not a gym bunny. Geeky, but able to talk about other things. As a bonus: gainfully employed, prone to wearing clean laundry, and regularly showered and shaved. What more could you want? (Okay, yes, there's probably a list.)
The highly non-standard disclaimers: I have a girlfriend. (She's missionista here on OKC.) We've never been monogamous nor are ever likely to be, but we've been dating for nearly twenty years, share an apartment and a child, and don't seem inclined to stop soon. We're not trolling for threesomes here (our tastes don't overlap much, and inasmuch as they do these days that itch is well-scratched), and if you want to be her friend that's between you and her— but being friendLY to her if you're ever in a room together is required. She's awesome, so this is usually not difficult.
Okcupid used to have a madlibs-style fill-in-the-blank self-summary in the form of "I am ____, ____ and ____." They killed those off a while back, but I was oddly proud of "I am binary, variable, and on the main sequence." If nerdy astronomy jokes are your style, we'll probably get along just fine.