O*mis"sion (?), n. [L. omissio: cf. F. omission. See Omit.] 1. The act of omitting; neglect or failure to do something required by propriety or duty.

The most natural division of all offenses is into those of omission and those of commission.

2. That which is omitted or is left undone.

• The act of omitting.
  
• The act of neglecting to perform an action one has an obligation to do.
  
• Something deleted or left out.
  
• Something not done or neglected.
  
• Grammar, the shortening of a word or phrase, using an apostrophe ( ' ) to replace the missing letters, often used to approximate the sound of speech or a specific dialect.
       six o'clock -- six of the clock
       The high school class of '69 -- 1969
       O'er there -- over there