Out of the common path; aside; -- used in composition, giving
   the meaning of something aside, secondary, or incidental, or collateral
   matter, a thing private or avoiding notice; as, by-line, by-place,
   by-play, by-street. It was formerly more freely used in composition
   than it is now; as, by-business, by-concernment, by-design,
   by-interest, etc.