The weapon(s) system(s) were the essential technological weaponry, used offensive and defensive purposes, found on starships, space stations, outposts and planets. They could be identified by their various weapons signature. (VOY: "The Swarm")
Standard weapon systems included technology as phaser arrays, phaser banks, tactical sensors, disruptor arrays, and torpedoes/photon systems. (ENT: "Sleeping Dogs"; DS9: "Defiant"; VOY: "Caretaker", et al.) The Minosian's Echo Papa 607 was considered to be their "proudest achievement: the ultimate in weapons system technology." (TNG: "The Arsenal of Freedom")
As the USS Enterprise created an emergent lifeform in 2370, the holodeck created several characters that Troi theorized to be individuals who "represent different aspects of the ship," stating for example, that "the gunslinger could be the weapon system." (TNG: "Emergence")