| 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. | Chemistry. 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. Compare trans- (def. 2). |
| cis- pref.
[Latin, from cis, on this side of; see ko- in Indo-European roots.] |
cis- pref.
Often cis- Having a pair of identical atoms or groups on the same side of a plane that passes through two carbon atoms linked by a double bond: cis-butene.
