Las

- acronym for Leaving After Sex

Which in this case refers to leaving a relationship with an individual after having sexual intercourse with said individual

Type 1
Girl 1: im so scared that james is totally gonna las on me

Girl 2: you're too hot for anyone to leave you dont worry bout it.

Type two
Girl 1: omg omg james and Brittney are totally gonna smash tonight.
Girl 2: i knooww but sucks becuase i feel like james is the type of guy to las out on a girl.

Girl 1: omg you're totally right about that.