Acronym for 'Wizz In My Pants'. Self explanatory. To urinate in one's own pants. Can be used in literal terms or as a figure of speech (for people who got dead scared of something)
Literal: Damn man! I got so drunk last night, I W.I.M.P.-ed!
Figurative: That movie was so scary I W.I.M.P.-ed out.
Stands for "Woe Is Me Poster". In social media, one who posts for the purposes of soliciting sympathy from followers or friends. Example, "Having a bad day." or "Can't seem to wake up."
That person's posts are not funny or witty, they're just whiney. They're a W.I.M.P.