The technique described in the question, "Picturing a pair of 'lips' to remember what an ellipse is," is an example of "Keywords". Using 'lips' to remember 'ellipse' is considered a method involving Keywords, a mnemonic device for aiding memory, rather than a rhyme.
A mnemonic device is a memory aid that helps individuals remember information.
In this case, using the image of lips provides a visual representation of the shape of an ellipse, aiding in recall.
Mnemonic devices can be helpful in remembering information across various subjects and grades.
When picturing a pair of 'lips' to remember what an ellipse is, this mnemonic device is best categorized as a form of Keywords.
Mnemonic devices, such as the example provided, involve the use of a word or term ('lips') that sounds similar to the concept being remembered ('ellipse'), where the sound or aspect of the keyword triggers the memory of the conceptual term.
This technique is different from Rhyming, which would involve recalling terms or concepts based on the end sound of two or more words.
Mnemonics such as using keywords can be a powerful tool in education, making it easier to recall mathematical shapes, formulas, or other educational content.