Eustachian tube /juˈsteɪʃən ˈtjuːb/ noun1 •In humans and other land vertebrates, a tube that links the nasopharynx to the cavity of the middle ear to allow the equalization of the pressure on both sides of the eardrum.Ice water trickled down my eustachian tubes, leaving a cold, bitter taste in my mouth. — 2016 formsEustachian tubes · eustachian tubes