Gosh darn it is an expression of frustration or disappointment, often used as a milder alternative to stronger profanity. The crossword solutions for this term are Tarnation (9 letters), DRAT (4 letters), CRUD (4 letters), NERTS (5 letters), Rats (4 letters), HECK (4 letters), and Ohrats (6 letters). All of these words are euphemisms for stronger profanities, and are used to express frustration or disappointment in a more socially acceptable way.