A plasma pistol was a pistol sized plasma weapon variety of firearm, used as a sidearm.
History and specifications[]
Plasma weapons were the standard firearm of the human species after gunpowder projectile weapons became obsolete. They could be found in civilian hands by 2152, indicating they were ubiquitous enough for civilian ownership. They were in turn eventually superseded by the phaser. United Earth Starfleet used these weapons in the 22nd century, prior to the adoption of phase pistols. Outdated EM-33 plasma pistols were deployed by the crew of the Enterprise (NX-01) during their maiden voyage, before Lt. Malcolm Reed, the ship's armory officer, distributed the newer phase pistol. (ENT episode: "Broken Bow")
Military Assault Command Organization forces deployed a rifle with similar superficial design features, which was likely also a plasma weapon, indicating that Earth's non-Starfleet civilian and military forces likely still used plasma weapons like the EM-33 for some time after their retirement by Starfleet. (ENT episode: "The Xindi")