A disruptor rifle was a weapon, a rifle modification of a disruptor. These weapons were used by Klingons, Romulans, and Cardassians. They gave off more energy than a disruptor pistol.
The Klingon version of this weapon had induction coils that could burn out. (DS9: "Honor Among Thieves")
The Romulan disruptor rifle went through a few changes. In 2368 their rifle was small and thin. By 2371 the rifle had been enlarged and given a much sleeker design. (TNG: "Unification I", "Unification II"; DS9: "Improbable Cause")
In the alternate reality in 2258, Hikaru Sulu and James T. Kirk used disruptor rifles to sabotage the Narada's drill when Chief Engineer Olson died. (Star Trek)
In the mirror universe of 2370, Quark tried to defend himself with a disruptor rifle but was overwhelmed by Klingons. (DS9: "Crossover")
The Cardassian disruptor rifle was a much simpler design than the Starfleet Type 3 phaser rifle. It had very few settings on it and fewer components than its alien counterparts. Major Kira Nerys said that it could be dragged through the mud and still fire. (DS9: "Return to Grace")