Merriam-Webster's Collegiate® Dictionary, 11th Edition
STAIN
I. verb see: distain
Date: 14th century
transitive verb to suffuse with color, discolor , soil ,
3. taint 3 , to bring discredit on , to color (as wood, glass, or cloth) by processes affecting chemically or otherwise the material itself, intransitive verb to receive a stain, stainable adjective stainer noun
II. noun
Date: 1557
1. a soiled or discolored spot, a natural spot of color contrasting with the ground, a taint of guilt ; stigma , a preparation (as of dye or pigment) used in staining: as, a dye or pigment capable of penetrating the pores of wood, a dye or mixture of dyes used in microscopy to make visible minute and transparent structures, to differentiate tissue elements, or to produce specific chemical reactions, stainproof adjective