Meaning of ester gum

es'ter gum"

Pronunciation: [key]
— Chem. Chem.
  1. any of several hard resins produced by the esterification of a natural resin, esp. rosin, with a polyhydric alcohol, chiefly glycerol: used in the manufacture of paints, varnishes, and lacquers.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.