This is the 1623rd most frequent German word.
unwahrscheinlich
Unlikely; improbable.
Here, 'unwahrscheinlich' is used as an adjective meaning 'unlikely,' describing the probability of an event happening.
Es ist unwahrscheinlich, dass es morgen regnen wird.
It is unlikely that it will rain tomorrow.
In this case, 'unwahrscheinlich' is applied to describe something that seems extraordinary or hard to believe in terms of authenticity or usual occurrence.
Die Geschichte klingt unwahrscheinlich, aber beeindruckend.
The story sounds improbable but impressive.
Here, 'unwahrscheinlich' functions as an intensifier meaning 'amazingly' or 'unbelievably,' modifying the extent of the adjective 'fast.'