The Collaborative International Dictionary of English v.0.48:

paintbrush \paint"brush`\ n.
   A brush used to apply paint.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

paintbrush
    n 1: a brush used as an applicator (to apply paint)

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "paintbrush":
   air brush, art paper, brush, camera lucida, camera obscura, canvas,
   chalk, charcoal, crayon, drawing paper, drawing pencil, drier,
   easel, fixative, ground, lay figure, maulstick, medium, paint,
   palette, palette knife, pastel, pencil, pigments, scratchboard,
   siccative, sketchbook, sketchpad, spatula, spray gun, stump,
   varnish



The Free On-line Dictionary of Computing (30 December 2018):

Paintbrush

    A Microsoft Windows tool for creating
   bitmap graphics.

   (1996-08-26)