eardrum UK /ˈɪəˌdɹʌm/US /ˈiɚˌdɹʌm/ noun1 •A thin membrane that separates the outer ear from the middle ear and transmits sound from the air to the malleus.Those exposed to the weapon experience sharp ear pain, disorientation and panic, security experts say. Prolonged exposure can cause eardrum ruptures and irreversible hearing damage. — 2025 formseardrums