Seconder

Noun

1. Something that lasts or takes a specified number of seconds.
2. The person who makes a second to a motion in any formal procedure, such as a parliamentary procedure.

   "He's been the seconder on many motions, but I don't think he's ever made a motion himself."

3. A Cub Scout serving as a second-in-command to a sixer.
4. A person who seconds; a person who climbs after the leader