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p.o.

  1. (in prescriptions) by mouth.
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Origin of p.o.

From the Latin word per ōs

P.O.

  1. parole officer.
  2. petty officer.
  3. postal (money) order.
  4. post office.
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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018