9 letters · 15 points in Scrabble
noun reflex pupillary dilation as a muscle pulls the iris outward; occurs in response to a decrease in light or certain drugs
originFrom Latin mydriasis, from Ancient Greek μυδρίᾱσις (mudríāsis, “undue enlargement of the pupil”), from μύδρος (múdros, “mass of red hot material in a forge”), possibly because the pupil is particularly bright or sparkling when dilated, or because of the red eye effect when exposed to a flash of light.
Etymology from Wiktionary, CC BY-SA 3.0