We don't have synonyms for stratis yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are stratus, stratic and statis.
(n) :
(meteorology) A principal, low-level cloud type in the form of a gray layer with a rather uniform base, usually not associated with precipitation, and capable of producing corona phenomena and a weak, uniform luminance; abbreviated St.
(n) :
(meteorology) A principal, low-level cloud type in the form of a gray layer with a rather uniform base, usually not associated with precipitation, and capable of producing corona phenomena and a weak, uniform luminance; abbreviated St.