grace note

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A musical note, especially an appoggiatura, added as an embellishment, printed in small type, and not counted in rhythm.

from The Century Dictionary.

• noun In music, a grace; especially, an appoggiatura. See grace, 6.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun music A musical note written in smaller print, with or without a slash through it, to indicate that its note value does not count as part of the total time value of the measure.
• noun figuratively Concerns of secondary importance to that which is of primary concern.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an embellishing note usually written in smaller size