happening by chance, unintentionally, or unexpectedly

a verdict of accidental death

the damage might have been accidental

incidental; subsidiary

the location is accidental and contributes nothing to the poem

(in Aristotelian thought) relating to or denoting properties which are not essential to a thing's nature

a sign indicating a momentary departure from the key signature by raising or lowering a note

horn parts are usually written without key signature, the necessary accidentals being added