A thought disorder in which a person replies to question in an oblique, tangential or irrelevant manner, without getting to the point. In effect, the person expresses one thought after another. He or she is unable to control the flow of his or her thoughts and speech, resulting in a speech to digress readily from one topic under discussion.
For example, when asked about the city he is from he may answer that he is from Iowa but really doesn’t know where his relatives are from so he is unsure if he is Irish or French. (Source: wikipedia)