C clefC clefn. Music A symbol indicating which line of a staff represents the pitch of middle C. On the bottom line it becomes the soprano clef, on the middle line the alto clef, and on the third line above the bottom the tenor clef.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.C clef n (Music, other) music a symbol (), placed at the beginning of the staff, establishing middle C as being on its centre line. See alto clef, soprano clef, tenor clef Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014C clef n. a movable musical clef locating middle C on the first, third, or fourth line of the staff. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.