An animal that includes escaped from the owner; a wandering pet whoever owner is as yet not known. An animal may not be an estray when from the range where it was raised, and allowed by its owner to operate. A lost pet whose owner is known to the party accessible is certainly not an estray.
Any valuable pet, perhaps not crazy, found wandering from its owner; a stray.
A tame creature, or important pet, as a horse, ox, or sheep, which is found wandering or without an owner; a beast supposed to have strayed from the power and/or inclosure of the owner.
Figuratively, everything with strayed far from its owner.