Engine gunk is a term used to describe the accumulation of dirt, oil, and other debris that can build up in an engine over time. The crossword solutions for this term are CRUD, which stands for 'Chunks of Residue Under Deposit'. This term is used to describe the buildup of material that can occur in an engine, such as oil, dirt, and other debris. This buildup can cause a decrease in engine performance and can even lead to engine failure if not addressed.