noun

1. 1. a solid, liquid, or gaseous substance made up of very small, insoluble particles (as single large molecules or masses of smaller molecules) that remain in suspension in a surrounding solid, liquid, or gaseous medium of different matter
   2. a state of matter consisting of such a substance dispersed in a surrounding medium: all living matter contains colloidal material, and a colloid has only a negligible effect on the freezing point, boiling point, or vapor pressure of the surrounding medium
2. the iodine-containing, gelatinous protein stored in the thyroid

Etymology: < Gr kolla, glue + -oid; coined by T. Graham (1805-69), Scot chemist