leger line

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

• noun A musical notation to inscribe notes outside the lines and spaces of the regular musical staves; a line slightly longer than the note is drawn parallel to the staff, above or below, spaced at the same distances as the notes within the staff.

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

• noun a short line; a notation for extending the range above or below the staff