The Oxford Thesaurus An A-Z Dictionary of Synonyms - omissionn.

1) non-inclusion, omitting, leaving out or off, excluding, eliminating, dropping, skipping; exclusion, exception, deletion, elimination, excision: The omission of your name from the list was a mistake. Allowing for inadvertent omissions, the inventory is complete. 2) failure, default, neglect, dereliction, oversight, shortcoming, negligence: She is being punished for her innocent omission in failing to notify the police while he is at liberty despite his deliberate commission of a crime.