Jungftak: A Persian bird, the male of which had only one wing on the right side, and the female only one wing on the left side; instead of the missing wings, the male had a hook of bone, and the female an eyelit of bone, and it was by uniting hook and eye that they were enabled to fly. Each, when alone, had to remain on the ground. (Webster's unabridged dictionary 1943)
Apparently, map and dictionary publishers sometimes include fictional entries as a preemptive strike against competitors who might copy and publish stolen content as their own. A sort of watermark of fabricated information and meanings.
Think about it, for would be copyright infringers these fictional entries are: landmines of the imaginary.
Also: what if the fictional entry enters into usage? Then it no longer becomes fictional...
In dictionaries and encyclopedias these fictional entries are called "mountweazels." On maps they are called "trap streets" and "paper towns."
I found out about "jungftak" because this dude called up a linguistics podcast called "A Way With Words" and confessed that he had been haunted by this one word for DECADES. That is what I'm talking about.