1. Open to more than one interpretation: an ambiguous reply.
2. Doubtful or uncertain: "The theatrical status of her frequently derided but constantly revived plays remained ambiguous" (Frank Rich).

Synonyms: These adjectives mean lacking clarity of meaning. Ambiguous indicates the presence of two or more possible meanings: Frustrated by ambiguous instructions, I was unable to assemble the toy.
Something equivocal is unclear or misleading: "The polling had a complex and equivocal message for potential female candidates" (David S. Broder).
Obscure implies lack of clarity of expression: Some say that Blake's style is obscure and complex.
Recondite and abstruse connote the erudite obscurity of the scholar: "some recondite problem in historiography" (Walter Laqueur). The students avoided the professor's abstruse lectures.
What is vague is expressed in indefinite form or reflects imprecision of thought: "Vague . . . forms of speech . . . have so long passed for mysteries of science" (John Locke).
Cryptic suggests a sometimes deliberately puzzling terseness: The new insurance policy is full of cryptic terms.
Something enigmatic is mysterious and puzzling: The biography struggles to make sense of the artist's enigmatic life.