bow thruster

Short definition from Wiktionary

Noun

1. 1
   A propulsion unit mounted in or on the bow of a vehicle: A sideways-pointing thruster mounted in a tunnel in the bow or under the bow in a pod, for increased maneuverability.
2. 2
   A propulsion unit mounted in or on the bow of a vehicle: A fixed or adjustable direction propeller unit mounted on the bow of an airship for increased maneuverability.