A disruptor is a common energy weapon in Star Trek. They are the preferred weapons of the Klingon and Romulan civilizations. Disruptors are scalable, ranging in size from sidearms to primary capital ship weapons.
While their operating principles are unclear, disruptors seem to perform much like phasers. While equally effective, the damage they inflict tends to be more mechanical in nature -- ripping or tearing of affected material -- than that of phasers (TNG, "Hero Worship").
Disruptors of either scale can fire pulses or continuous beams.
- "It's not just an effective weapon. It's... vicious. It tears a body apart... and very slowly by your phaser standards."
-- Kivas Fajo describing a Veron-T disruptor, TNG "The Most Toys"