Meaning at top speed, as in "I'm going flat-out down the highway when..." Also used to indicate an absolute state of something, or something being completely within a state: "Skydiving is flat-out cool," or "that guy was flat-out scary." In this same vein, it can be used in place of an explicative.

Y'know, if you log in, you can write something here, or contact authors directly on the site. Create a New User if you don't already have an account.