Drooping of the upper eyelid caused by muscle paralysis and weakness

• Eyelid ailment
• Drooping eyelid, medically

Wikipedia Word definitions in Wikipedia
Ptosis is a drooping or falling of the upper eyelid . The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to amblyopia . If severe enough ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
1743, from Greek ptosis , literally "falling, a fall," also "the case of a noun," nominal derivative of piptein "to fall" (see symptom ). In English, especially of the eyelid. Related: Ptotic .

WordNet Word definitions in WordNet
n. drooping of the upper eyelid caused by muscle paralysis and weakness [also: ptoses (pl)]

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Ptosis \Pto"sis\, n. [NL., fr. Gr. ? a falling.] (Med.) Drooping of the upper eyelid, produced by paralysis of its levator muscle.