Pronunciation: ra-se'mik, -sem'ik
Denoting a mixture of optically active compounds that is itself optically inactive, being composed of an equal number of dextro- and levorotatory substances, which are separable. Those compounds chracterized by two or more chiral centers and internal compensation (an internal line of symmetry), and are therefore not separable into d or l (or + and -) forms, receive the prefix meso-) (meso-cystine).
Search Stedman's Medical Dictionary
Examples: glitazone, GI cocktail, etc.