Decoding the Missing Letters

 Rebus Challenge: Decoding the Missing Letters

 A rebus is a pictogram that represents a word, phrase, or saying. For example, "Ci ii" represents "See eye to eye." What word or phrase does the following rebus represent: O_ER_T_O_?

Answer: Painless operation.

Explanation: The letters missing in O_ER _T _O_ (OPERATION) spell out PAIN. Thus, "painless" operation.