Merriam-Webster Collegiate Dictionary - colloid

 noun  Etymology: International Scientific Vocabulary coll- + -oid  Date: circa 1852  1. a gelatinous or mucinous substance found normally in the thyroid and also in diseased tissue  2.  a. a substance that consists of particles dispersed throughout another substance which are too small for resolution with an ordinary light microscope but are incapable of passing through a semipermeable membrane  b. a mixture consisting of a ~ together with the medium in which it is dispersed smoke is a ~  • ~al adjective  • ~ally adverb