It is a neologism (humorous, is not even an anglicism) to qualify as correct a word that would also be a neologism or even a forced lexicon that sounds correct by parasintesis; in a broad sense it means good, valid, acceptable. It was coined as cromulent by David X. Cohen for a chapter of the Simpsons where legitimating the non-existent term embiggen (that would be associated with enlarged), and from there was repeated and became popular.