This warning occurs in conjunction with issue F403, 'from module import *' used. It means that the variable name could be undefined, but flake8 cannot be sure because it also could also be imported in the star imports.

Confirm that the variable is defined in the star imports. If it is, explicitly import it instead of importing *. If not, then define the variable.

Anti-pattern

from mymodule import *

def print_name():
    print(name)  # name could be defined in mymodule

Best practice

Either explicitly import name…

from mymodule import name

def print_name():
    print(name)

…or define name.

from mymodule import *

def print_name(name):
    print(name)