What is track marks?

Strips of brownish discoloration that can often be found in the undergarments being worn by someone with a 'less-than-tidy' anus.

Damn it all. I just bought these briefs last week and they are already trashed with track marks.

track marks - video

can often mean the scars from shooting up. can also mean scars from cutting yourself.

-She always wears long sleeves to cover her track marks.
-She shoots up?
-Naw man, she cuts herself.
-Oh, less cool man.

the line of bruised needle holes in the arm of a junky produced as he shoots up at a slightly higher point on his arm each time.

she never wears short sleeves because she doesn't want anyone to see her track marks