Definition of tabby:
(n) :
a kind of waved silk, usually called watered silk, manufactured like taffeta, but thicker and stronger. The watering is given to it by calendering; a mixture of lime with shells, gravel, or stones, in equal proportions, with an equal proportion of water. When dry, this becomes as hard as rock
(adj) :
having a wavy or watered appearance; as, a tabby waistcoat; brindled; diversified in color; as, a tabby cat