Define Get Under Meaning

“ GET UNDER THE SHEALTER NOW! It’s dropping bombs!

-Hey Harold, that guy just totally took a greasy shit all over Jim's shaggin wagon.
Yeah, he fuckin' got under.

-Dude dont be such a little pussy.
The fuck you talkin bout bro? I've been getting under all day.

-Check out my knuckles Chuck. I think they might be broken. I got into a fight with a niglet last night and took him to the cleaners.
Oh you fuckin' got under? Yeah look at that.

My boss is really good at getting under my skin with her constant reminding...

He was trying to get under my skin but it didn't work

Someone curses at you, you say "Get Under Your Bed Mate"