What does "incidental" mean?

Incidental: Happening, as an occasional event, without regularity; coming without design; casual; accidental; hence, not of prime concern; subordinate; collateral; as, an incidental conversation; an incidental occurrence; incidental expenses. By some, religious duties . . . appear to be regarded . . . as an incidental business. Rogers. See Accidental. -- In`cen*den"tal*ly, adv. -- In`cen*den"tal*ness, n. I treat either or incidentally of colors. Boyle.

Additional senses

  1. 2.An incident; that which is incidental; esp., in the plural, an aggregate of subordinate or incidental items not particularized; as, the expense of tuition and incidentals. Pope.

Sources