1. a prefix occurring in loanwords from Latin meaning “on the near side of ” (cisalpine); on this model, used in the formation of compound words (cisatlantic).
2. Chem.a specialization of this denoting a geometric isomer having a pair of identical atoms or groups attached on the same side of two atoms linked by a double bond. Cf. trans- (def. 2).
Commonwealth of Independent States.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.