Something with ambiguity is unclear. Think about the sentence, "Jill saw the man with binoculars." If you are wondering whether Jill or the man had the binoculars, you are noticing the ambiguity, or the double meaning, of this sentence.
Lawyers word contracts to avoid ambiguity, but in doing so prevent anyone who is not a lawyer from understanding what they have written! If you can't choose between two decisions because both seem somehow wrong, you are dealing with moral ambiguity. Imagine if a friend who has helped you out many times asks you to cheat. It's wrong to cheat but it also seems wrong not to help someone who has been there for you.