1968 25 Jan. 196/2 One of the ship's tanks is selected to serve as a slop tank... The tanks to be cleaned are washed in turn and washings are pumped continuously into the top of the slop tank.
1979 F. Forsyth ix. 223 She had sixty giant tanks, or holds... One of these was the slop tank, to be used for..gathering the slops from her fifty crude-carrying cargo tanks.