Hit the sack is an idiom which means to go to bed or to RETIRE for the night. The crossword solutions for this term are CRASH (5 letters), RETIRE (6 letters), RETIRED (7 letters), and TURNIN (6 letters). CRASH is a verb meaning to suddenly fall asleep, RETIRE is a verb meaning to withdraw from one's job or position, RETIRED is an adjective describing someone who has withdrawn from their job or position, and TURNIN is a verb meaning to go to bed.