Via Celtics press release:

The Boston Celtics announced today that they have requested waivers on forward Marcus Landry.

Landry, a 6'7 forward, was acquired by the Celtics along with guard Nate Robinson on February 18. Landry appeared in one game for the Celtics after he was acquired from New York and played three minutes. In 18 combined games for New York and Boston this season Landry averaged 2.4 points and 1.1 rebounds in 6.2 minutes per game.

Not sure the reasoning behind this.  He wasn't going to crack the rotation one way or the other but I'm not sure if this saves them much money.  We'll update if we get any quotes or rationale.