When you make up a word in order to rhyme it with an existing one. The term is derived from Dr Seuss an author who wrote
children's books like Cat in the
Hat and The Grinch.
Dr. Seuss is probably the only person to ever gt away with Seussing because he was awesome like that, but if you do it, you
suck.
You may find something like this in a Dr Seuss book.
The
animal wrangler fought back the
beast with his amazing shcrizzlefangler!
Now, how to use it in a sentence....
Rapper: Yo! rollin' up in my fine ass jeep, bouncin' my head like a verzkizical shmeep!
Poet: Dude, at least try to rhyme, you're just Seussing right now.