variants or petri- or petro-
1
a
: stone : rock
petrescent
Petricola
petrogenesis
b
: petroleum
petroporphyrins
2
: of or relating to the petrous portion of the temporal bone and
petrohyoid

Word History

Etymology

Middle French petr-, petri- & Latin petr- & New Latin petro-, from Greek petr-, petro-, from petros stone & petra rock

The Ultimate Dictionary Awaits

Expand your vocabulary and dive deeper into language with Merriam-Webster Unabridged.

  1. Expanded definitions
  2. Detailed etymologies
  3. Advanced search tools
  4. All ad-free

Discover what makes Merriam-Webster Unabridged the essential choice for true word lovers.

Start Your Free Trial Now

Browse Nearby Words

Cite this Entry

“Petr-.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/petr-. Accessed 4 Feb. 2026.

Kids Definition

petr-

combining form
variants or petri- or petro-
1
: stone : rock
2
: petroleum
petrochemical
Etymology

Greek petros "stone" and petra "rock"

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

More from Merriam-Webster