Definition of O in US English:

O

abbreviation

  • 1Ocean.

  • 2(in prescriptions) a pint.

  • 3Octavo.

  • 4October.

  • 5US Ohio.

  • 6Old.

  • 7Ontario.

  • 8Oregon.

  • The chemical element oxygen.

Pronunciation

O

/ō//oʊ/