slacks noun[plural only]1 •Semi-formal trousers which are less formal than those that are part of a suit but nowadays are considered suitable casualwear in most offices. (Takes a plural verb even when referring to a single pair; may be referred to as a pair of slacks.)Not five minutes later, Zooey, with his hair combed wet, stood wet, stood barefoot at the washbowl, wearing a pair of beltless dark-gray sharkskin slacks, a face towel across his bare shoulders. — 1957
