The horizontal line at the top part of tights, where there begins a boxer-shaped darker colored section. When this line becomes visible, you know that your shorts / skirt / clothes are probably too short and not very appropriate; you've crossed the slut line.
by strawberrycrisp May 14, 2011
Where a woman, presumably a slut, makes an assertion, either verbally or by actions, towards her lack of promiscuity during the course of a sexual act with a complete stranger.
Dude, she was sucking on his dick five minutes after meeting him and was then uncomfortable with removing her bra as he was moving too fast, thats a I'm not a slut line if i ever heard one.
by Slaalaikum August 20, 2009