Aaron's rod \Aar"on's rod`\ ([^a]r"[u^]nz r[o^]d`). [See Exodus
vii. 9 and Numbers xvii. 8]
1. (Arch.) A rod with one serpent twined around it, thus
differing from the caduceus of Mercury, which has two.
[1913 Webster]
2. (Bot.) A plant with a tall flowering stem; esp. the great
mullein, or hag-taper, and the golden-rod.
[1913 Webster]