[pto.sis] n, pl pto.ses [NL, fr. Gk ptosis act of falling, fr. piptein] (1743): a sagging or prolapse of an organ or part; esp: a drooping of the upper eyelid
PTOSIS
Meaning of PTOSIS in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012