If you fluster someone, you make them feel nervous and confused by rushing them and preventing them from concentrating on what they are doing. The General refused to be flustered She was a very calm person. Nothing could fluster her. + flustered flus·tered She was so flustered that she forgot her reply. to make someone nervous and confused by making them hurry or interrupting them. in a fluster nervous and confused because you are trying to do things quickly