Webster's English Dictionary

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undo

un.do \.*n-'du:, '*n-\ vt 1: to open or loose by releasing a fastening (as 
   a lock) : UNTIE  2: to make of no effect or as if not done : make null : 
   REVERSE  3a: to ruin the worldly means, reputation, or hopes of  3b: to 
   disturb the composure of : UPSET  3c: SEDUCE  : to come open or apart  - 
   un.do.er n