A negative disposition displayed by a possessor of gay identity. Typical attributes include finger pointing, high pitched sarcasm, and a supreme sense of entitlement accompanied by sanctimony.
Seated at a cafe discussing which celebrity you most closely resemble.
Civilian: I think you'd be Helena Christenson
Victim: Oh really, thanks!
Gattituder (overhearing and then interrupting): Yeah, maybe if a truck had run over her face.
The badass attitude someone gets while chewing gum virgorously open-mouthed.
Marci nearly bit my head off for asking a simple question because she had gattitude.