noun
An aside, an act of straying from the main subject in speech or writing.
(generally uncountable) The act of straying from the main subject in speech or writing, (rhetoric) particularly for rhetorical effect.
(obsolete) A deviancy, a sin or error, an act of straying from the path of righteousness or a general rule.
(now rare) A deviation, an act of straying from a path.
(astronomy, physics) An elongation, a deflection or deviation from a mean position or expected path.