One who is of bitch nature as they attempt to invade another's buffer seat. This person is usually of jackass nature as well or known to be full of shit.
Guy 1: Hey did you see that jackass who sat next to me in seminar? Who the fuck does that?
Guy 2: Yeah that guy was a completebuffer seat bitch.
The person in a group who isn't a leader, on the contrary, because this person is a bitch, all this person does is take orders and defer responsibility to the actual leader. For this reason, this person never has to deal with anything that resembles a "high pressure" situation which- at least in their minds- is good because a high pressure situation would cause this person to crack and undoubtedly fail.