The Collaborative International Dictionary of English v.0.48:
Amphisbaena \Am`phis*b[ae]"na\, n. [L., fr. Gr. ?; ? on both
ends + ? to go.]
1. A fabled serpent with a head at each end, moving either
2. (Zool.) A genus of harmless lizards, serpentlike in form,
without legs, and with both ends so much alike that they
appear to have a head at each, and ability to move either
way. See Illustration in Appendix.
Note: The Gordius aquaticus, or hairworm, has been called
an amphisbaena; but it belongs among the worms.