a combining form meaning “rock,” “stone,” used in the formation of compound words: petrology.
Also petri-; especially before a vowel, petr-.

Origin of petro-

< Greek, combining form of pétra rock, pétros a stone

Definition for petro- (2 of 2)


a combining form meaning “petroleum,” “the extraction and export of petroleum,” used in the formation of compound words: petrochemistry; petropower.

Origin of petro-

extracted from petroleum Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for petro-


before a vowel petr-

combining form

indicating stone or rockpetrology
indicating petroleum, its products, etcpetrochemical
of or relating to a petroleum-producing countrypetrostate

Word Origin for petro-

from Greek petra rock or petros stone
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for petro-



Rock; stone; stone-like hardness:petrous.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.