WordWeb Online

1. Loosening the ties that fasten something
   "the tying of bow ties is an art; the untying is easy";
   - undoing, unfastening

1. Undo the ties of
   "They untied the prisoner";
   - unbrace, unlace
    
2. Cause to become loose
   "untie the knot";
   - undo

Type of: alter, change, laxation, loosening, modify, undo

Antonym: tie