The term 'Yucky Stuff' can be described by the crossword solutions GOO (3 letters), SLIME (5 letters), GOOK (4 letters), SLOP (4 letters), GOOP (4 letters), GLOP (4 letters), and CRUD (4 letters). These words all refer to substances that are unpleasant to touch, smell, or look at. GOO is a sticky, slimy substance, while SLIME is a thick, slippery liquid. GOOK is a thick, viscous liquid, and SLOP is a sloppy, wet mixture. GOOP and GLOP are similar to GOO and SLIME, but are thicker and more viscous. Finally, CRUD is a general term for dirt, grime, or other unpleasant substances.