user-variable-p

user-variable-p is an alias for `custom-variable-p' in `custom.el'.

(user-variable-p VARIABLE)

This function is obsolete since 24.3;
use `custom-variable-p' instead.

Return non-nil if VARIABLE is a customizable variable.
A customizable variable is either (i) a variable whose property
list contains a non-nil `standard-value' or `custom-autoload'
property, or (ii) an alias for another customizable variable.