Similar word to incidental:
accidental, accompanying, adventitious, ancillary, attendant, by-the-way, casual, chance, circumstantial, coincidental, concomitant, concurrent, contingent, contributing, contributory, fluke, fortuitous, irregular, nonessential, occasional, odd, random, secondary, subor
accidental, accompanying, adventitious, ancillary, attendant, by-the-way, casual, chance, circumstantial, coincidental, concomitant, concurrent, contingent, contributing, contributory, fluke, fortuitous, irregular, nonessential, occasional, odd, random, secondary, subor