The act of two or more males spending an evening in a hot tub or jacuzzi together without any female counterparts present.
Erik invited the boys over for a night of man-tubbing and PBR.
A large, formidable dude.
Have you seen that two tub man that's bouncing down at Tony's?
Damn it feels great to hit up the poor man's hot tub "shower" and relax after a day on the mountain.