a sixty-fourth note.
1850–55; hemi- + demisemiquaver
hemidemisemiquaver. Dictionary.com. Dictionary.com Unabridged (v 1.1). Random House, Inc. http://dictionary.reference.com/browse/hemidemisemiquaver (accessed: February 20, 2009).
Jill noticed her symphony date had a nervous tick. His facial hairs would vibrate in a wave like fashion on one side of his face during the louder bass notes. There was one particular section of rapid kettle drum strikes where she almost burst out laughing; The 64th note beat sent his mustache in to a hemidemisemiquaver quiver!