Rudolph W. Giuliani’s statement on Wednesday that he was uncertain whether waterboarding, a simulated drowning technique, was torture drew a sharp rebuke yesterday from Senator John McCain, who said that his failure to call it torture reflected his inexperience.

“All I can say is that it was used in the Spanish Inquisition, it was used in Pol Pot’s genocide in Cambodia, and there are reports that it is being used against Buddhist monks today,” Mr. McCain, who spent more than five years in a North Vietnamese prison camp, said in a telephone interview.

Of presidential candidates like Mr. Giuliani, who say that they are unsure whether waterboarding is torture, Mr. McCain said: “They should know what it is. It is not a complicated procedure. It is torture.”

Mr. Giuliani said on Wednesday night at a forum in Davenport, Iowa, that he favored “aggressive questioning” of terrorism suspects and using “means that are a little tougher” with terrorists but that the United States should not torture people. On the question of whether waterboarding is torture, however, Mr. Giuliani said he was unsure.