Incapacitated by alcohol is an appropriate term and describes the vast majority of alcohol related rape. People who are either fully unconscious or unable to voice consent or lack thereof. If she literally cannot say "no", it's rape.
Despite what tumblr or /r/mensrights says, meeting a girl at a party and drinking with her until she is no longer safe to drive a car but can have a conversation with you, then having sex that she enjoys and is clear about enjoying throughout, is neither damaging to her nor a significant risk to you of being accused of rape.
A tiny subset of women have accused men in such scenarios of rape--those cases are not the norm.
It is important to maintain communication with a partner who has been drinking though.
More or less this, I guess.
I'm not going to entertain the notion that I've raped my wife, for example, just because she came home intoxicated and looking to bone after she had some drinks on a night out with her girlfriends.
That's not the same as humping some chicken who's passed out in a pool over her own vomit. Or climbing naked into the shower with a drunk chick who's throwing up her guts. ---