Pronounced 'IH-dah', it is an acronym for "I'd Do Her." Essentially it is a rating system for hot girls, with a fairly complex yet simple, relatable, and customizable set of paramaters. The idea is that you can talk about hotness of girls in a public place without alerting their suspicions, and it illustrates a better idea of the hotness of a girl than the traditional 1-10 rating system.

IDH: Baseline doable girl. Hot but nothing special.

DIDH: Definitely I'd Do Her. Really hot girl that you'd pounce on given the chance. Boobs poppin out and really hot body.

IDH + n B: where B means beers and 'n' is a variable of amount of beers. So "IDH plus 3 B" would be a girl who would be doable after three beers.

IDH +/- n Y: Where Y is a number of years. So if you see a girl who would be hot once they hit 18, you'd say "IDH plus 4 Y". Likewise, an older woman that was probably really hot 15 years ago but is now just a cougar would be "IDH minus 15 Y"

Special cases:

TIDH/Badoobadaboob: "Tits I'd Do her" - basically this IDH is mainly hot because she has a really nice, unignorable pair of punching bags.

IFH: I'd Fuck Her. Pronounced "IF-ah". Denotes a girl so hot you'd just fuck the shit out of her. Almost always directed at a slut you'd really have no respect for other than for the fact that she's got a bangin body and a pussy begging to get fucked to pieces.

MILF IDH: This is a really hot girl who is young but also happens to have borne children.

IDH MILF: ...