noun. A symbol ( — ) used in writing and printing to indicate a break in thought or sentence structure, to introduce a phrase added for emphasis, definition, or explanation, or to separate two clauses.

noun. Alternative spelling of em dash.

"Before I do, though, I’d just like to point out to anyone whose eyes might have lit up at the sight of the word emdash: it’s NEVER correct to use an emdash in a manuscript; standard format requires a doubled dash with a space at either end."