Haematoxylin \H[ae]m`a*tox"y*lin\ (-t[o^]ks"[i^]*l[i^]n), n. [See {H[ae]matoxylon}.] (Chem.) The coloring principle of logwood. It is obtained as a yellow crystalline substance, {C16H14O6}, with a sweetish taste. Formerly called also {hematin}. [1913 Webster]