petr-
1.
variant of
petro-
1.
before a vowel:
petrous.
British Dictionary definitions for
petr-
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