They’re usually just called quills or, more specifically, defensive quills. On an African crested porcupine, the tougher ones on the back and hindquarters are the stabbing quills used for defense.

Quick scoop

The porcupine’s most useful “stabbing” quills are the short, thick hindquarter quills that it uses when it backs into a predator. The longer quills along the head and back help it look bigger and more threatening.

Plain-language version

If someone asks for the common name, quills is the right answer. If you want the more descriptive term, say defensive quills or stiff defense quills.

TL;DR: African crested porcupines don’t have a special separate name for “stabbing quills” in everyday use — they’re simply called quills , especially the defensive quills on the rear.