By Allen Kanfer. Source: https://www.poetryfoundation.org/
poetrymagazine/browse?contentId=28478
Glossary: to ad-lib: If you ad-lib something in a play or a speech, you say something
which has not been planned or written beforehand.
(https://www.collinsdictionary.com/dictionary/english/ad-lib)
The conjunction in “as it leaps” has the same function as in the
sentence