(Chem.) A prefix (also used adjectively) signifying rose-red; specifically used to designate certain rose-red compounds (called roseo-cobaltic compounds) of cobalt with ammonia. Cf. Luteo-. [ 1913 Webster ]

‖n. [ NL., dim. of L. rosa a rose. ] (med.) A rose-colored efflorescence upon the skin, occurring in circumscribed patches of little or no elevation and often alternately fading and reviving; also, an acute specific disease which is characterized by an eruption of this character; -- called also rose rash. -- Ro*se"o*lous a. [1913 Webster]