Relating to atoms or groups attached to a cyclic structure but not themselves cyclic; e.g., the -CH3 group of toluene. ... Compare: endocyclic. ... (05 Mar 2000) ... 
Type: Term Pronunciation: ek′sō-sī′klik, -sik′lik Definitions: 1. Relating to atoms or groups attached to a cyclic structure but not themselves cyclic, the methyl group of toluene.