from The American Heritage® Dictionary of the English Language, 4th Edition
- transitive v. Archaic To go back over (one's course); retrace.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. To retread (one's steps) in the opposite direction; to walk back.
from the GNU version of the Collaborative International Dictionary of English
- transitive v. To tread back; to retrace.
from The Century Dictionary and Cyclopedia
- To tread back; go back through in the same steps; retrace.
un- + tread (Wiktionary)