[spec.trum] n, pl spec.tra or spectrums [NL, fr. L, appearance--more at specter] (1671) 1 a: a continuum of color formed when a beam of white light is dispersed (as by passage through a prism) so that its component wavelengths are arranged in order b: any of various continua that resemble a spectrum in consisting of an ordered arrangement by a particular characteristic (as frequency or energy): as (1): electromagnetic spectrum (2): radio spectrum (3): the range of frequencies of sound waves (4): mass spectrum c: the representation (as a plot) of a spectrum
2. a: a continuous sequence or range "a wide ~ of interests" b: kinds of organisms associated with a particular situation (as an environment) or susceptible to an agent (as an antibiotic)