accidental
//ˌæk.sɪˈden.təl//
Adjective
accidentalCanonical form
1
Happening by chance or unexpectedly; not planned or intended.
The fire was accidental, not deliberate.
2
Occurring as a minor or secondary consequence; incidental.
The discovery was accidental to the main research project.
Antonym
Noun
1
A sign in music notation indicating a temporary change in pitch (sharp, flat, or natural) not indicated by the key signature.
The composer used several accidentals to create an unexpected harmonic shift in the melody.