Someone who makes plans but never follows through by not returning phone calls or ignoring them. Also they cannot be trusted with anything and are usually lurkin around shit.
Yeah she said we were going to hang out this weekend, but she ignored me all week. What a shadester.
When a guy is being totally shady for no reason at all and you do not know why but it bothers the hell out of you and they do not have a goodexplanation for why they were being shady.