Pyroclasts (or "tephra') are any volcanic fragment that was hurled through the air by volcanic activity. A pyroclastic eruption is one in which the great majority of activity involves fountaining or explosions. A pyroclastic deposit is the resulting layer or pile of material that has fallen to the ground by one or many pyroclastic eruptions. A pyroclastic rock is the hardened, solidified, or compressed version of an originally loose pyroclastic deposit.
Spatter (a type of pyroclast) is globs of lava thrown through the air that land while still molten.
Photograph by T.T. English, U.S. Geological Survey, April 30, 1982
The word is a combination of “pyro” or fire, and “clastic” or made up of many pieces.