n.1 (in full ichneumon wasp) any small hymenopterous insect of the family Ichneumonidae, depositing eggs in or on the larva of another insect as food for its own larva.
2 a mongoose of N. Africa, Herpestes ichneumon, noted for destroying crocodile eggs.
Etymology: L f. Gk ikhneumon spider-hunting wasp f. ikhneuo trace f. ikhnos footstep