caduceus

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A herald's wand or staff, especially in ancient times.
2. n. Greek Mythology A winged staff with two serpents twined around it, carried by Hermes.
3. n. An insignia modeled on Hermes's staff and used as the symbol of the medical profession.

Century Dictionary and Cyclopedia

1. n. In classical mythology, the rod or wand borne by Hermes, or Mercury, as an ensign of authority, quality, and office. It was originally merely the Greek herald's staff, a plain rod entwined with fillets of wool. Later the fillets were changed to serpents; and in the conventional representations familiar at the present day the caduceus is often winged. The caduceus is a symbol of peace and prosperity, and in modern times figures as a symbol of commerce, Mercury being the god of commerce. The rod represents power; the serpents represent wisdom; and the two wings, diligence and activity. In heraldry it is blazoned as a staff having two serpents annodated about it, mutually respectant, and joined at the tails; it is a rare bearing.

Wiktionary

1. n. The official wand carried by a herald in ancient Greece and Rome, specifically the one carried in mythology by Hermes, the messenger of the gods, usually represented with two snakes twined around it.
2. n. A symbol (☤) representing a staff with two snakes wrapped around it, used to indicate merchants and messengers, and also sometimes as a symbol of medicine.

GNU Webster's 1913

1. n. (Myth.) The official staff or wand of Hermes or Mercury, the messenger of the gods. It was originally said to be a herald's staff of olive wood, but was afterwards fabled to have two serpents coiled about it, and two wings at the top.

WordNet 3.0

1. n. an insignia used by the medical profession; modeled after the staff of Hermes