2.A substance through which an effect is transmitted from one thing to another; as, air is the common medium of sound. Hence: The condition upon which any event or action occurs; necessary means of motion or action; that through or by which anything is accomplished, conveyed, or carried on; specifically, In animal magnetism, spiritualism, etc., a person through whom the action of another being is said to be manifested and transmitted. "Whether any other liquors, being made mediums, cause a diversity of sound from water, it may be tried." "I must bring together All these extremes; and must remove all mediums."
3.An average. (R.) "A medium of six years of war, and six years of peace."
5.(Paint.) The liquid vehicle with which dry colors are ground and prepared for application.
6.(Microbiology) A source of nutrients in which a microorganism is placed to permit its growth, cause it to produce substances, or observe its activity under defined conditions; also called culture medium or growth medium. The medium is usually a solution of nutrients in water, or a similar solution solidified with gelatin or agar.
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