I. flus ‧ ter 1 /ˈflʌstə $ -ər/ BrE AmE verb [transitive]
to make someone nervous and confused by making them hurry or interrupting them:
Don’t fluster me, or I’ll never be ready on time.
II. fluster 2 BrE AmE noun British English
in a fluster nervous and confused because you are trying to do things quickly