n. & v.
n. 1 the culmination or climax (of endeavour, success, etc.). 2 a natural peak. 3 a small ornamental turret usu. ending in a pyramid or cone, crowning a buttress, roof, etc.
v.tr. 1 set on or as if on a pinnacle. 2 form the pinnacle of. 3 provide with pinnacles.
[ ME pinacle f. OF pin(n)acle f. LL pinnaculum f. pinna wing, point (as PIN, -CULE) ]