A made up word. An imaginary lexicon construction. A
spontaneous utterance perhaps used by reflex or surprise.
A word formed at random from a reaction similar to an
onomatopoeia.
Farnuculent does exist as a real word, however, it is defined as a fabricated word.
I didn't understand the
drunk man at the bar slurring his speech and mumbling farnuculent phrases. I think he was inventing insults and uttering them under his
alcoholic breath.
Stubbing
one's toe in the middle of the night on the way to the bathroom might induce a phrase of phonetic peculiarity such as, "eeyaag!" This word, if used, would be farnuculent.