"Cycle" is a bit non-specific.
It can mean several things.
It can mean:

A complete body of teachings from beginning to end eg.
Longchen Nyingtik, Dudjom Tersar, or Nam Cho

or it can mean

a complete series of teachings and practices from
one of the above such as Dudjom Lingpa's Chod
(which includes a ngondro, the main practice and
dzogchen practices) or Longchen Nyingtik's Yeshe Lama
(which contains thousands of pages of Dzogchen practices),
or a Collection of Lama, Yidam or Dakini practices.

It could also mean the central practices of a lineage:
such as its three roots and main protectors taken together.

So when using the word cycle, the implication is something
complete rather than just one segement or text. A text comes from a cycle.