n. [ Rose + aniline. ] (Chem.) A complex nitrogenous base, C20H21N3O, obtained by oxidizing a mixture of aniline and toluidine, as a colorless crystalline substance which forms red salts. These salts are essential components of many of the socalled aniline dyes, as fuchsine, aniline red, etc. By extension, any one of the series of substances derived from, or related to, rosaniline proper. [ 1913 Webster ]