n.
Pronunciation: präp- ' t ō -s ə s, pr ō - ' t ō -
Function: noun
Etymology: New Latin, from Late Latin, falling forward, from Greek propt ō sis, from propiptein to fall forward, from pro- forward + piptein to fall ― more at PRO- , FEATHER
Date: 1676
: forward projection or displacement especially of the eyeball