octothorp

from the GNU version of the Collaborative International Dictionary of English.

• noun A typographic symbol (#) having two vertical lines intersected by two horizontal lines. It is also called the crosshatch, hash, numeral sign and number sign; in the U. S. it is commonly called the pound sign, especially to designate the symbol as used on digital telephone dials, but this can be confusing to Europeans who think of the pound sign as the symbol for the British pound. It is commonly used as a symbol for the word number.

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

• noun Alternative spelling of octothorpe.