Icky residue is a term used to describe a variety of unpleasant, sticky substances. SLIME, SCUM, and GUNK are all words used to describe icky residue. SLIME is a five-letter word that refers to a thick, slimy substance, often found in nature. SCUM is a four-letter word that describes a thin, film-like layer of dirt or other material that forms on the surface of a liquid. GUNK is also a four-letter word that refers to a thick, sticky, and often smelly substance. All three words can be used to describe icky residue.