minus sign

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

• noun Mathematics The symbol −, as in 4 − 2 = 2, that is used to indicate subtraction or a negative quantity.
• noun Chemistry The same symbol, used to indicate levorotatory rotation of polarized light.

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

• noun mathematics The symbol − or - used to denote the operation of subtraction and to indicate that a number is negative.

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

• noun a sign indicating the operation of subtraction