Definition of "accidental" []

• Occurring unexpectedly, unintentionally, or by chance. (adjective)
• Music Of or relating to an accidental. (adjective)
• A property, factor, or attribute that is not essential. (noun)
• Music Any of various signs that indicate the alteration of a note by one or two semitones or the cancellation of a previous sign. (noun)
• Music A note that has been marked with such a sign. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Reporters soon adopted the phrase accidental attack, a description that frustrated Pentagon officials, who felt it minimized the ferocity of the sustained assault that had killed or injured two out of every three men on board."
• "Nor again (b) will ‘white’ have another term accidental to it, e.g. ‘musical’."
• "In 2007, Greg Parks was prepping his kids for the Florida state test, but in what he calls an accidental peek at the test, the middle-school math teacher noticed a troubling choice of words: Instead of asking kids about the volume of a can — the example he and the textbooks had been using — the test asked about the volume of a swimming pool."