"Cryptid" is a word coined by cryptozoologists (no surprise). It refers to any animal which is reported but not confirmed, including never-caught species and presumed-extinct ones. Michael Woodley here examines the use and misuse of the term. He rejects Dr. Charles Paxton's advice, which is that theorizing about cryptids is pointless, and we should use reports, not hypothesized creatures, as the basics for theorizing.
COMMENT: I see Charles' point. For example, cryptozoologists are not really studying a "cryptid" called sasquatch, they are studying reports of large unclassified primate. Sometimes, there is something to be said for focusing the discussion with at least a general outline of a "cryptid," but it's unscientific to name a solution, to the exclusion of other solutions, when there is no animal in hand.
This reminded me of how the late Grover Krantz aimed to spark scientific discussion when he published a paper naming a specific presumed-extinct species, Gigantopithecus blacki, as the source of sasquatch reports. The problem is that he named it based on footprints when we have only teeth and jawbones of Gigantopithecus and no one can say what the feet looked like. Almost no one in the anthropological community accepted such a reach, and it did not do anything to burnish the reputations of cryptozoology in the "mainstream" scientific world, nor the reputation of Krantz (who was a genuine expert with well-respected work in human evolution.) Still, Krantz was never sorry he did it: he thought he achieved his primary objective.