Definition from Wiktionary, the free dictionary
pinnacle (plural pinnacles)
- The highest point.
- A tall, sharp and craggy rock or mountain.
- (figuratively) An all-time high; a point of greatest achievement or success.
- (architecture) An upright member, generally ending in a small spire, used to finish a buttress, to constitute a part in a proportion, as where pinnacles flank a gable or spire.
- Some renowned metropolis / With glistering spires and pinnacles around.
- See also Wikisaurus:apex
tall, sharp and craggy rock or mountain
See also 
- to put something on a pinnacle
- to build or furnish with a pinnacle or pinnacles
- (Can we find and add a quotation of T. Warton to this entry?)
- pinnacle in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
- pinnacle in The Century Dictionary, The Century Co., New York, 1911