cis-: Meaning and Definition of

cis-

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. 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).

C.I.S.

1. Commonwealth of Independent States.