jammer

Short definition from Wiktionary

Noun

1. 1
   Any device used to jam radio reception.
2. 2
   A musician who jams.
3. 3
   A device (e.g. a jumar) which will slide along a rope in one direction but not the other, used in rock-climbing, caving etc.
4. 4
   A player who attempts to score points by making their way past other players.
5. 5
   A player of the massively multiplayer online game Animal Jam (now either the app so named, formerly Animal Jam – Play Wild!, or the desktop game renamed Animal Jam Classic).