The Probert Encyclopaedia of Architecture

PINNACLE

In architecture a pinnacle is an architectural member, upright, and generally ending in a small spire. They are used to finish a buttress, to constitute a part in a proportion, as where pinnacles flank a gable or spire, and the like.
Pinnacles may be considered primarily as added weight, where it is necessary to resist the thrust of an arch, etc.
Research Pinnacle