from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. To unfasten (something tacked).
- v. To remove the tack from.
from the GNU version of the Collaborative International Dictionary of English
- transitive v. To separate, as what is tacked; to disjoin; to release.
from The Century Dictionary and Cyclopedia
- To separate (that which is tacked); disjoin; loosen; release.
un- + tack (Wiktionary)