Definify.com
Webster 1913 Edition
Amphitheatre
{ 
, Amˊphi-the′a-ter
,Amˊphi-the′a-tre
, }Noun.
 1. 
An oval or circular building with rising tiers of seats about an open space called the arena. 
☞ The Romans first constructed amphitheaters for combats of gladiators and wild beasts. 
2. 
Anything resembling an amphitheater in form; as, a level surrounded by rising slopes or hills, or a rising gallery in a theater.