slacks

vapaa-ajan housut puhekieltä puhekieltä Semi-formal trousers that are less formal than those part of a suit but suitable for wearing in most offices and therefore nowadays no longer considered casual trousers. (Takes a plural verb even when referring to a single pair; may be referred to as a pair of slacks)
1957, w:J. D. Salinger|J. D. Salinger, "Zooey", in, 1961, w:Franny and Zooey|Franny and Zooey:

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.