The navigational deflector is the dish-shaped emitter at the front of a starship that sweeps space debris out of the vessel's path at high speed.
Even tiny particles become dangerous at warp, so a starship projects a beam from its main deflector to push aside dust and debris ahead of it. The dish is tied into the ship's sensors and power systems, which makes it a natural point for improvised modifications.
Engineers have repeatedly turned the deflector into a powerful tool. The Enterprise-D tried to fire a concentrated energy beam from its dish at a Borg cube, though the Collective adapted before the blast could destroy it. Voyager's crew also reconfigured their deflector many times to emit special beams and pulses.