When you are having a good time in the trenches in WW 1; When you are chilling with your bools in general; when you are in the trenches and you are cleaning your feet to keep clean.
When you don't know what the fuck to do with your life so you just go with the flow and act like you're not stressed as shit and avoid all responsibilities
"I'm just Boulin it"
Translates into "I'm really stressed but I'm just going to not do anything about it and like go with the flow"