having sex, intercourse, fucking; to fuck a girl. Straight up, but hard; knocking the bottom out of it
I bought my girl a new outfit last weekend. She looked so hot dressed in it that I had to gut check her before leaving for the party.
A test of will power, courage, fortitude, etc. Rarely does it involve any physical strength or skill, instead being an almost entirely mental challenge. First heard in the US Army, but has spread through usage amongst veterans.
Jumping off the cliff at night, into the darkened water, with the pretty girl watching: it's a gut check. See what you're made of.