1) To murk someone via a cuss/diss/boiment/par
2) To get excited/become excitable about something minute
3) To portray general outlandishness
4) To produce fantastic lyrical performance in a rap/spit.
Person 1: (Laughs) Your shape up is nuts! (Laughs) How can you go to the barbers and come out looking worse than before like Edward scissor hands cut your hair! Par!
Person 2: (Laughs) Allow it, you're GOING IN on him!
Person 1: Jheeeeezeee!! I'm that guy!! I got an A in my GCSE Food technology! Suwoo!!
Person 2: Rah, you're GOING IN, still. These times nobody cares about Food Tech, you ain't Ainsley Harriet.
*Guy walks past wearing hot pants*
Person 1: (Laughs hysterically) What is that bruddah doin' wearing them mad tight pants! He's GOING IN with the hot pants!
*Listening to American Rapper J Cole:*
"Aye nigga I'm the best man, as if my best friend was getting married,
Even with my eye closed I'm something like a visonary,
Paint you a perfect picture nigga this is picturnary,
Man they goin have to put my picture in the dictionary,
Right next to real then put your picture right next to fictionary..."
Person 1: Jheeze, J Cole GOES IN on this track!
Ah-hah! I might gotta take my shirt off (yeah, kid...)
I like that one (uh-huh, go in, go in!)
Weezy before his verse on A Milli: "Mac I'm going in"