pin ‧ na ‧ cle /ˈpɪnək ə l/ BrE AmE noun
[ Date: 1200-1300 ; Language: Old French ; Origin: pinacle , from Late Latin pinnaculum , from Latin pinna 'wing, wall around the top of a castle' ]
1 . [singular] the most successful, powerful, exciting etc part of something:
the pinnacle of academic achievement
pinnacle of
She had reached the pinnacle of her political career.
at the pinnacle of something
The bank was then at the pinnacle of England’s financial system.
2 . [countable] literary a high mountain top
3 . [countable] a pointed stone decoration, like a small tower, on a building such as a church or castle