A combination of "skinny" and "attitude"; the loud, boisterous, obnoxious arrogance often displayed by skinny "beautiful people" with low to no intelligence and/or small sexual attributes such as breasts or penises'. This is very common; many thin people often try to compensate for their insecurity with their mental and/or sexual triviality by loudly and cruelly berating "overweight" people.
"oh no he didn't just say that, that skinny assmoron on this talk show better just get over his tiny penis and own up to his skinnitude"
Skankitude is a measure of a girl's sexual desirability, taking into account her style of clothes, her sexual experience, and her level of promiscuity, in other words, her skankiness. Some skankitude is integral in any girl, but too much will of course be dangerous for everyone involved.
"Yo dude, that girl is hot!"
"Yeah, but her skankitude is off the charts."