The crossword solution for the term IRK with 'AT' is GNAW. GNAW is a verb meaning to bite or chew on something persistently, usually with the teeth. It is often used to describe the behavior of animals such as rodents, but can also be used to describe a person's frustration with a situation. The term IRK is an informal verb meaning to irritate or annoy someone. Therefore, the crossword solution GNAW can be used to describe the feeling of being irritated or annoyed.