"Seropus" is not a commonly known word, and its spelling can be rather tricky. In IPA phonetic transcription, it is pronounced /sɪˈrəʊpəs/. The first syllable is pronounced as "sih" with a short "i" sound, the second syllable is "roh" with a long "o" sound, and the final syllable is "puhs" with a "p" sound and an "s" ending. It is important to remember that some words can have unconventional spellings, so it is always helpful to consult a dictionary or language resource.
Purulent serum; pus largely diluted with serum.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.