any of a family (Lymantriidae) of moths whose caterpillars are covered with long tufts of hair: many, as the gypsy moth, are destructive pests of certain trees
See tussock moth in American Heritage Dictionary 4
noun
Any of various dull-colored moths of the family Lymantriidae, the caterpillars of which have tufts of hair along the back and are often destructive to deciduous trees.