Backward Pass
1. Any pass not forward is regarded as a backward pass. A pass parallel to the line is a backward pass. A runner may pass backward at any time.
2. A backward pass that strikes the ground can be recovered and advanced by either team.
3. A backward pass caught in the air can be advanced by either team.
4. A backward pass in flight may not be batted forward by an offensive player.
NFL.com Rule book
1. Any pass not forward is regarded as a backward pass. A pass parallel to the line is a backward pass. A runner may pass backward at any time.
2. A backward pass that strikes the ground can be recovered and advanced by either team.
3. A backward pass caught in the air can be advanced by either team.
4. A backward pass in flight may not be batted forward by an offensive player.
NFL.com Rule book