What is Heather Mac?
1.
A certain type of woman who is a stick figure yet doesn't gain weight even though she enjoys MaCdonalds or some type of fast food store very, very much.
"oh god, did you see that Heather MaC today as she came out of Burger King? She is the size of a stick!"
"you should all be Heather MaC 's if you eat that much fast food"
See