popping hot

To test positive for something bad (e.g. drugs, STDs, steroids, etc.). Specifically refers to the testing method of urinalysis, wherein the person being tested has to pee in a specimen cup.

Ex. 1
Military recruit: I want to enlist so I have something to do after high school, but they won't let me 'cause I keep popping hot for weed.
Ex. 2
Friend 1: Chris ever tell you what happened after he hooked up with that tinder girl a few weeks ago?
Friend 2: Yeah, he ended up popping hot for gonorrhea. I felt bad for him, but he should've known better than to go raw.