1. verb To make a mistake, often an embarrassing one. A noun or pronoun can be used between "flub" and "up." Oh man, I totally flubbed up that intro—I was trying to read the teleprompter, but then I started tripping over my words.

2. verb To cause someone to make a mistake. A noun or pronoun can be used between "flub" and "up." Come on, let me try again—the cat running across the street totally flubbed me up that time!

3. noun Such a mistake. In this usage, the phrase is often hyphenated. Oh man, this is a colossal flub-up. What am I going to tell the boss?