"#", ascii character 35.

Common names: number sign; pound; pound sign; hash; sharp; crunch; hex; intercal: mesh. Rare: grid; crosshatch; octothorpe; flash; itu-t: square, pig-pen; tictactoe; scratchmark; thud; thump; splat.

The pronunciation of "#" as "pound" is common in the US but a bad idea; commonwealth hackish has its own, rather more apposite use of "pound sign" (confusingly, on British keyboards the pound graphic happens to replace "#"; thus Britishers sometimes call "#" on a US-ASCII keyboard "pound", compounding the American error). The US usage derives from an old-fashioned commercial practice of using a "#" suffix to tag pound weights on bills of lading. The character is usually pronounced "hash" outside the US.