#it
Short hand for pound it. Easier to write online this way. Kind of silly to use though because you can't actually pound over the internet.
Jim: dude I found a summer job, it's gon be ill
Frank: oh woooord, #it
Jim: ...*pound*
Frank: *pound*
Jim: god I feel lame
Frank: oh woooord, #it
Jim: ...*pound*
Frank: *pound*
Jim: god I feel lame