1660s, "body fluid," from Latin latex (genitive laticis) "liquid, fluid," probably from Greek latax "dregs," from PIE root *lat- "wet" (cf. Middle Irish laith "beer," Welsh llaid "mud, mire," Lithuanian latakas "pool, puddle," Old Norse leþja "filth"). Used 1835 to mean "milky liquid from plants." Meaning "water-dispersed polymer particles" (used in rubber goods, paints, etc.) is from 1937. As an adjective by 1954, in place of clasically correct laticiferous.
The colorless or milky sap of certain trees and plants, such as the milkweed and the rubber tree, that hardens when exposed to the air. Latex usually contains gum resins, waxes, and oils, and sometimes toxic substances.
A manufactured emulsion of synthetic rubber or plastic droplets in water that resembles the latex of plants. It is used in paints, adhesives, and synthetic rubber products.