Slp or Slipi when said verbaly is the abbreviation of the phrase "slaying like pit" In this case the "pit" is refering to the american actor Brad Pit.
Slp is a synonyme for the slang word slay and is used the same way
Seductive Loosening of the Penis Gland. Other terms for this include wanking, masturbating, jerkin the gherkin, or arm wrestle the one-eyed vessel or rub the magic one-eyed wonder weasel. Every man does it and every man has a different name for it.
Person 1: Hey man, why didn't you come over last night?