Ambiguous means "having several possible meanings," "open to differing interpretations": "I don't understand your answer; it's ambiguous." Equivocal is closely related in meaning to ambiguous, but it is more often used to signify "not determined," "of doubtful nature," "open to a double interpretation": "The judge found the loyalty of this citizen to be equivocal." Ambiguous is applied only to written or spoken statements; equivocal can apply to speech, writing, actions, and ideas. Unequivocal, directly opposite in meaning to equivocal, means "clear," "having only one possible meaning or interpretation": "His refusal to pay the bill is unequivocal."
Dictionary of problem words and expressions. Harry Shaw. 1975.