(in the plural, nautical, dated) sailors' breeches ending just below the knees or above the ankles, worn mainly in XVIII century
2012, Nelson's navy, by Philip Haythornthwaite, page 26:The original "slops" were voluminous breeches of about knee length, reminiscent of 17th century "petticoat breeches", worn with stockings; these continue to be depicted as late as 1790s, but trousers, first introduced as slop-clothing in 1720s, were more functional and more popular.
(in the plural, dated) The dirty wastewater of a house.(A direct quote from: 1897Universal Dictionary of the English Language, v 4 p 4310)