severe UK /sɪˈvɪə/US /sɪˈvɪɹ/ adjective3 •so bad or so strong that it causes real trouble or painIn the severer cases of hookworm the patient sometimes has an appetite for soil, paper, hair, clay, chalk, starch, and other unpalatables. — 1934 •Strict or harsh. •Sober, plain in appearance, austere. formsmore severe · severer · most severe · severest