Fall through is a term used to describe a situation in which a plan or project fails to be completed. The crossword solutions for this term are FAIL (4 letters), FIZZLE (6 letters), and FOUNDER (7 letters). FAIL is an action that is the opposite of succeeding, FIZZLE is a verb meaning to FAIL to fulfill expectations, and FOUNDER is a noun meaning to FAIL completely. All three words can be used to describe a situation in which a plan or project falls through.