- fog, fogginess, murk, murkiness - an atmosphere in which visibility is reduced because of a cloud of some substance
--1 is a kind of atmosphere, atmospheric state
--1 has particulars: fug - cloudiness, murkiness, muddiness - the quality of being cloudy
--2 is a kind of opacity, opaqueness
--2 has particulars: turbidity, turbidness; haziness, mistiness