Incidental is most often used in the sense "being likely to ensue as a chance or minor consequence," or "minor" (as in "there were some incidental expenses that I paid myself").

INCIDENTAL definition: 1. less important than the thing something is connected with or part of: 2. directly connected…. Learn more.

Incidental definition: happening or likely to happen in an unplanned or subordinate conjunction with something else.. See examples of INCIDENTAL used in a sentence.

Definition of incidental adjective from the Oxford Advanced Learner's Dictionary. incidental (to something) happening in connection with something else, but not as important as it, or not intended. …

Occurring or likely to occur as an unpredictable or minor consequence: "the principle that even annoying, intrusive, and offensive speech is to be protected by the courts and tolerated by the public …