A plasma grenade is an explosive device.
In the year 2268, Cervantes Quinn had a pack of plasma grenades stored on the Dulcinea. He had hoped that they would make a difference against the approaching Klingons. (VAN - Declassified novella: The Stars Look Down)
In 2366, the Bajoran Resistance detonated a plasma grenade on the Promenade, injuring Skrain Dukat in an assassination attempt. Odo arrested Ishan Chaye, Jillur Gueta and Timor Landi for the crime and they were executed by the Cardassians. It was later discovered the three were innocent and could not have been the ones who threw the plasma grenade. (DS9 episode: "Things Past")