A mag chick is one of two things:
1) A chick so ugly that you would rather read a magazine than watch while she blows you
2) A chick so ugly that you would rather beat her over the head with a maglight than let her get near your junk.
Hey, I heard that your date is a mag chick, so i got you a magazine just in case.
Dude, thats a total mag chick! Get me the flashlight, quick!