1) Annulled 2) Annulled or erased 3) Brought to naught 4) Canceled 5) Cancelled 6) Dealt a severe blow 7) Destroyed 8) Detached 9) Disassembled 10) Disconnected 11) Disentangled 12) Fixed a word-processing error 13) Loosened 14) Loosened a knot 15) Opened 16) Past tense of undo 17) Removed ties 18) Reversed 1) Erased 2) Loosened 
• imp. of Undo.