An exothermic reaction is a chemical reaction that releases heat.
When Deep Space 9 personnel attempted to seal a subspace rupture with a pulse wave torpedo in 2369, Chief Miles O'Brien reported an exothermic reaction pattern within the phenomenon that neutralized the pulse waves. (DS9: "If Wishes Were Horses")
In 2378, Seven of Nine characterized a fire made by a Ventu girl on Ledos as an exothermic reaction. (VOY: "Natural Law")
While fleeing Denaxi Depot with the USS Protostar crew in 2384, Thadiun Okona remarked that using chlorine trifluoride would give their cargo trolley "one heck of an exothermic kick". (PRO: "Crossroads")