Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A gray, fine-grained volcanic rock consisting chiefly of plagioclase feldspar and one or more mafic minerals.

from The Century Dictionary.

  • noun A volcanic rock of wide-spread occurrence, especially in the Cordilleran region of North America.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Min.) An eruptive rock allied to trachyte, consisting essentially of a triclinic feldspar, with pyroxene, hornblende, or hypersthene.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun geology A class of fine-grained intermediate igneous rock, of volcanic origin, containing mostly plagioclase feldspar.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a dark grey volcanic rock

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[After the Andes.]

Examples

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