a short article in a newspaper or magazine placed alongside a main article and containing additional or explanatory material:useful sidebars spotlight personnel or historical background [as modifier]:some kind of sidebar story
a secondary, additional, or incidental thing; a side issue:nut collecting has become a commercial sidebar to most black walnut plantations [as modifier]:one of the festival’s sidebar series
(also sidebar conference) (in a court of law) a discussion between the lawyers and the judge held out of earshot of the jury.
sidebar in other Oxford dictionaries
Definition of sidebar in the US English dictionary