any remains, impression, or trace of a living thing of a former geologic age, as a skeleton, footprint, etc.
a markedly outdated or old-fashioned person or thing.
a linguistic form that is archaic except in certain restricted contexts, as nonce in for the nonce, or that follows a rule or pattern that is no longer productive, as the sentence So be it.
—adj.
of the nature of a fossil: fossil insects.
belonging to a past epoch or discarded system; antiquated: a fossil approach to economics.