Sentence:  Some referred to the toilet as the "<WSD>groover</WSD>" in honor of the old days when there had been no toilet seat. Instead people would sit directly on the top of the ammo can, leaving telltale grooves in their skin 
Meaning of the word marked with <WSD> tags:  A small portable toilet often used on multiday river trips in protected wilderness areas, so named because the original versions were metal boxes whose rims left a groove in the skin of the user.