Plasma flare (device)
A plasma flare was a low-cost, low-yield plasma-based device.
Plasma flares were one of the components in a biogenic weapon delivery system. In 2370, Starfleet planted disinformation among the Maquis suggesting that the Cardassians were assembling such a weapon in the Demilitarized Zone. The last components of the weapon were to be isomiotic hyposprays, quarantine pods, and plasma flares, being carried on a Yridian freighter. (TNG: "Preemptive Strike")
In 2376, a band of con artists led by Dala, pretending they were from the USS Voyager, sold Varn defective photon torpedoes. When Varn confronted them with the fact, describing the torpedoes as "worthless [and] no better than plasma flares," Dala suggested that maybe he "didn't arm them properly." (VOY: "Live Fast and Prosper")