(n) :
an artists brush used in oil and acrylic painting with a long
ferrule and a flat, somewhat tapering bristle head; a
neologism intended as a positive-sounding
umbrella term to describe various kinds of non-religious and non-superstitious people. (There is a Wikipedia article on this usage.)
"definition A person whose world view is free of
supernatural and
mystical elements. The ethics and actions of a bright are based on a
naturalistic world view. (2003, Paul Geisert and Mynga Futrell)"