I don't have access to my office library, but Jastrow's Dictionary (p. 1238) tells me that this is an Greek word (prosopon) that means "face." It appears in Hebrew and (here) Aramaic transcription with the same meaning. It can also mean the front side of an embroidered piece. And it can mean a sculpture of a human face.
I hope the discoverers publish a photo.
For more on the archaeology of Zipori (Sepphoris/Tzipori/Tzippori/Zippori - I keep finding new spellings!), see here and links (cf. here, here, and here).
UPDATE: Ah ha, the Jerusalem Post has a photo: Talmud comes alive in 1,800-year-old marble face found in Galilee. Similar artifacts have been uncovered over the years in several locations in Israel, including Caesarea and Beit Shean (Rossella Tercatin). It is indeed a a marble sculpture of a face with the mouth forming a fountain.
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