When a person doesn't show up for plans with friends, or informs them of nonattendance at the last minute.
Hey Dan, you want to go to the club on Saturday? Don't be a pin out
or I'll be pissed.
Dude, why'd you pin me out
on Saturday? I waited at the club for over an hour.
Don't invite Dan to another outting, he always pins out
What, Dan didn't show up again? I told you not to invite him, he's a pinner
Well I thought he just pinned you out