Webster's Revised Unabridged Dictionary · 1913

Gyracanthus

Gyracanthus (jir`ȧ*kan"thus) , noun

[New Latin, from Greek gyro`s round + 'a`kanqa spine.]

(Paleontology) A genus of fossil fishes, found in Devonian and carboniferous strata; -- so named from their round, sculptured spines.