Nonce word

Etymology

From "nonce," which arose through a medieval misdivision: the Middle English phrase “for then anes” (for the one purpose) was reanalyzed as “for the nonce.” A nonce word is thus literally a word made “for the once.”

noun phrase · /NONSS wurd/
A word coined for a single occasion, not intended to enter general use.
What it names
The ephemeral, one-off coinage — a word invented on the spot to fill an immediate need — as a category of its own.
Example
In her poem she invented “glimmerish” as a nonce word, never expecting anyone else to use it.
Related idea
Distinct from a neologism, which is a new word that may catch on and spread; a nonce word is meant to be disposable. Compare the hapax legomenon, which is defined by appearing only once in a body of text — a matter of attestation rather than intent.