The 33-year-old Smith has not been in the NFL this season. In 2013, he was with the Cincinnati Bengals, whose offensive coordinator then was current Redskins coach Jay Gruden.
Smith takes the roster spot vacated by Derek Carrier, who went on injured reserve Tuesday after tearing ligaments in his right knee in Washington's 24-21 victory at Chicago.
Smith has played for four NFL teams since 2005, making 163 catches in 121 games, with 13 touchdowns.
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