incidental

Short definition from Wiktionary

Adjective

1. 1
   Loosely associated; of limited relevance except indirectly; only accidentally related.
2. 2
   Existing tangentially, being a byproduct, a tangent, or a likely consequence.
3. 3
   Occurring by chance.
4. 4
   Entering or approaching, prior to reflection (more frequently incident).

Noun

1. 1
   Minor items, not further defined. Incidental expense.
2. 2
   Something that is incidental.