petro-1

1.
a combining form meaning “rock,” “stone,” used in the formation of compound words:
petrology.
Also, petri-; especially before a vowel, petr-.
Origin
< Greek, combining form of pétra rock, pétros a stone

petro-2

1.
a combining form meaning “petroleum,” “the extraction and export of petroleum,” used in the formation of compound words:
petrochemistry; petropower.
Origin
extracted from petroleum
British Dictionary definitions for petro-

petro-

combining form
1.
indicating stone or rock: petrology
2.
indicating petroleum, its products, etc: petrochemical
3.
of or relating to a petroleum-producing country: petrostate
Word Origin
from Greek petra rock or petros stone
Word Origin and History for petro-

before vowels petr-, word-forming element used from 19c., from comb. form of Greek petros "stone," petra "rock" (see petrous).

word-forming element used from mid-20c. to mean "of or having to do with petroleum products," from petroleum.

petro- in Medicine

petro- or petri- or petr-
pref.
Rock; stone; stone-like hardness: petrous.