double sharp definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a sign ( or ) placed before a note to show that it is to be raised two semitones
double sharp definition by American Heritage Dictionary
A symbol ( t/k ) placed before a note to indicate that it is to be raised by two semitones.