The crossword solution for the term 'I KNEW IT ALL ALONG!' is ALONG, which is a five-letter word. ALONG is an adverb that means 'in a continuous line in the same direction' or 'in the same direction as something else.' It can also be used to mean 'for a long time, ' which is likely the intended meaning in this context. The phrase 'I knew it all ALONG!' implies that the speaker had knowledge of a situation before it was revealed to others, and that they were right all ALONG.