(1) Doubtful or uncertain especially from being obscure or indistinct. (2) Unclear in meaning because of being understandable in more than one way.
Example:
Successful politicians are good at giving ambiguous answers to questions on controversial issues.
Ambiguous comes from the Latin verb ambigere, "to be undecided," which in turn includes the verb agere, "to drive." Something that is ambiguous drives the observer in two directions. When we speak of eyes as being of an ambiguous color, we mean that we cannot decide which color they are -- blue or green? The ambiguity of the smile of Mona Lisa makes us wonder what she's thinking about. An ambiguous order is one that can be taken in at least two ways. An order to "shut up!," on the other hand, may be very rude, but at least it's unambiguous.