heterocyclic
Concise Oxford English Dictionary © 2008 Oxford University Press:
heterocyclic /ˌhɛt(ə)rə(ʊ)ˈsʌɪklɪk, -ˈsɪklɪk/
▶adjective Chemistry denoting a compound whose molecule contains a ring of atoms of at least two elements (one of which is generally carbon).
'heterocyclic' also found in these Oxford entries:

