Flight of ideas can be a symptom of either a manic or a hypomanic episode, as well as other mental disorders. The name sounds like it's something experienced in thoughts, but it actually has to do with speaking rapidly and jumping from one topic to another.

I had a friend with bipolar I disorder who displayed classic flight of ideas in her speech. She'd talk nonstop and would, for example, go from talking about her new dishwasher to when she bought her china to a cute little store she...