What does -rnus mean in Latin?

-rnus, a suffix, means “suffix forming adjectives”.

How do you pronounce -rnus?

In classical Latin, [r.nʊs]; in ecclesiastical (church) Latin, [r.nus].

suffix

Classical[r.nʊs]Ecclesiastical[r.nus]

From earlier *-rinos, from Proto-Italic *-zinos, from -nus or from some -r- or -s- stem + -nus. Metanalysis of this suffix led to its free use.

What does -rnus mean in Latin?: -rnus, a suffix, means “suffix forming adjectives”.
How do you pronounce -rnus?: In classical Latin, [r.nʊs]; in ecclesiastical (church) Latin, [r.nus].