A critical period of time characterized by a heightened pressure to succeed, usually at or near the end of a given situation or undertaking. Okay, we've got two minutes to tie the game—it's crunch time, guys!
A period when pressure to succeed is great, often toward the end of an undertaking. For example, It's crunch time-we only have two more days to finish. This term employs crunch in the sense of "a critical situation or test." [Slang; 1970s]