Of the nature of phlegm; watery; aqueous: as, phlegmatic humors.Generating or causing phlegm.Abounding in phlegm; lymphatic; hence, cold; dull; sluggish; heavy; not easily excited to action or passion; apathetic; cool and self-restrained: as, a phlegmatic temperament. See temperament.Synonyms Frigid, impassive, unsusceptible. See apathy.