pinnacle

Concise Oxford English Dictionary © 2008 Oxford University Press:
pinnacle/ˈpɪnəkl/

▶noun

• 1 a high pointed piece of rock.

• 2 a small pointed turret built as an ornament on a roof.

• 3 the most successful point: the pinnacle of his career.

– derivatives
pinnacled adjective.

– origin ME: from OFr., from late L. pinnaculum, dimin. of pinna ‘wing, point’.