pyroclastic adjective 1noun 1forms 1 adjective1 •Mostly composed of rock fragments of volcanic origin or comminuted during an eruption.Within sixty seconds, the entire area was razed by pyroclastic material with a temperature of nearly two thousand degrees Fahrenheit. — 2022 noun1 •A rock mostly composed of rock fragments of volcanic origin.The basic volcanics are altered andesites, porphyritic diabases and andesites, and various pyroclastics. — 1897 formspyroclastics
