Illustrated Glossary of Organic Chemistry

Tetracyclic: A cyclic molecule having four rings.


A steroid is typically tetracyclic, having three six-membered
rings (rings A, B, and C) and one five-membered ring (ring D).
In cholesterol (shown here) the rings are fused.
  
This is tetracene, a polycyclic aromatic hydrocarbon
(PAH) having four fused benzene rings.