Plasma cannon

Plasma cannons were a form of directed energy cannon weaponry. On Starfleet vessels, they were the precursors to phase cannons. Plasma cannons fired a plasma discharge in the form of a beam or a burst similar to the plasma bullets fired by hand-held plasma weapons, but much bigger in size. 

History
In the early- to mid-22nd century, Earth Cargo Service freighters were commonly equipped with low-yield turrets, often referred to as "popguns", designed only to break up asteroids and meteors. Earth Y class freighters were typically equipped with a single plasma cannon and J class ships with two turrets. The captains of these freighters, however, would often upgrade the cannons for more powerful ones the first chance they got. To achieve a weapons lock, the target had to be within a nine kilometer range. 

The was equipped with several plasma cannons during the first days of its mission, but was eventually upgraded with the more advanced phase cannons. Enterprise's Shuttlepod 1 was equipped with dual plasma cannons. These plasma cannons had a range of less than ten kilometers. 

In the mid-22nd century, Nausicaan pirates also utilized fore and aft plasma cannons on their raiders. 

In an alternate timeline, Vosk, the leader of the Na'kuhl, offered Nazi Germany plasma cannons and plasma rifles in exchange for materials to build a temporal conduit.

In the mirror universe, in 2155, the Terran Empire still used plasma cannons on starships.