Meaning of ACCIDENTAL in English
adj. & n.
adj. 1 happening by chance, unintentionally, or unexpectedly. 2 not essential to a conception; subsidiary.
n. 1 Mus. a sign indicating a momentary departure from the key signature by raising or lowering a note. 2 something not essential to a conception. accidentally adv.
[ ME f. LL accidentalis (as ACCIDENT) ]
Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012