The sentence "He was ambiguous" is correct and usable in written English.
You can use it when referring to a person, situation, or statement that is unclear or open to interpretation. For example, "The CEO's response to the team's questions was ambiguous; nobody was sure what she meant."
He was ambiguous about whether he still truly believed in a democratic form of communism; Leszek Kolakowski, the exiled philosopher, rightly described that as "fried snowballs".
He was ambiguous about the consequences for the president's new policy, should Mr. Arafat be re-elected in a new and free election as the Palestinian leader, saying, "We will deal with the circumstances as we find them".
Gen. Colin L. Powell set off a furor in 1995 when he was ambiguous about whether he was selling his memoir, "My American Journey," or beginning a presidential campaign.
There were also chinks in his broadly impressive Commons performance on July 20th that could hint at trouble to come: he was ambiguous about whether he had ever discussed News Corp's now-abandoned bid for total control of BSkyB, a broadcaster it already part-owns, during private conversations with Mrs Brooks.
He's ambiguous purely for plot purposes.
After the sale, writer doesn't feel the house is really his -- he is ambiguous about committing himself to France; he misses the U.S.
What's interesting about the incubus is that he's ambiguous in terms of whether he's a female wet dream or a figure of rape and terror, and also whether he's real or imaginary.
In a second dissent, Justice Samuel A. Alito Jr. focused on the language of the federal law, which he said was ambiguous.
"From my perspective it was a first date, but he thought it was ambiguous," she said.
Since Congress did not specify what it meant, the statute was ambiguous, he said, adding, "We interpret ambiguous criminal statutes in favor of defendants, not prosecutors".
"He says our letter was ambiguous but I had language experts verify what we'd written beforehand and it was quite clear," he says.
