noun: a musical notation that makes a note sharp or flat or natural although that is not part of the key signature
adjective: without intention (especially resulting from heedless action)
Example:Accidental poisoning.
adjective: associated by chance and not an integral part
Example:Poetry is something to which words are the accidental, not by any means the essential form- Frederick W.
Robertson.
adjective: occurring or appearing or singled out by chance
Example:Their accidental meeting led to a renewal of their friendship.