from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Composed chiefly of rock fragments of volcanic origin.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Mostly composed of rock fragments of volcanic origin
- n. A rock mostly composed of rock fragments of volcanic origin
from The Century Dictionary and Cyclopedia
- Formed by volcanic agencies, or in the process of being erupted: applied to volcanic breccia or to any angular or comminuted material of igneous origin.
- n. A pyroclastic rock.
From pyro- + clastic, from Ancient Greek πῦρ (pur, "fire"), and κλαστός (klastos, "broken"). (Wiktionary)