• (a.) Having hydrocephalus.
Hy`dro·ceph'a·lous adjective Having hydrocephalus. ' Hydrocephalous offspring.' G. Eliot. 
The accumulation of fluid in the ventricles of the brain. The head may appear to be large and dome shaped. Many small breeds of dogs have a degree of hydrocephalous that is normal for the breed. Severe hydrocephalous damages brain tissue.