ETYM Cf. French accidentel, earlier accidental.
1. Occurring or appearing or singled out by chance; SYN. casual, chance.
2. Without intention; especially resulting from heedless action; SYN. inadvertent.
3. Associated by chance and not an integral part;- Frederick W. Robertson.
Music sign indicating that the following note is to be raised or lowered, as a departure from the key signature.
In music notation, a sharp, flat, or natural sign preceding a note which changes the pitch of the note by a semitone up (sharp), down (flat), or back to normal (natural).
Music written in “black-note” keys may require the rarer double sharp and double flat signs indicating a change in pitch of a full tone. + prikaži više

Coincident.
1. Resulting from a coincidence
2. Occurring or existing at the same time

ETYM Cf. French inadvertant. Related to In-, and Advert.
Unintentional; not deliberate; occurring by oversight.

1. Not intentional; SYN. unplanned, unwitting.
2. Without deliberate intent; SYN. unwilled.

Not aware or knowing; SYN. unaware.