My very excellent mother just served us nine pizzas is a mnemonic for remembering the order of the planets in our solar system (including poor, downgraded Pluto, of course). What kind of mnemonic is this?

verbal/rhythmic organization

Explanation:

verbal / rhythmic organization -

Mnemonics are the method by which any phrase or piece of information can be learned easily and efficiently in the form of a rhythm, is referred to as the verbal / rhythmic organization.

This is a type of short cut method, by which any long statement can be learned in short form.

Hence, from the given scenario of the question,

The correct term is verbal / rhythmic organization.