Meaning
膾 (なます, Nama-su) is Namasu, a Japanese food (pickled salted or fermented).
What is Namasu?
Namasu is a dish consisting of thinly sliced uncooked vegetables ( nama ) and seafood, marinated in rice vinegar ( su ) for several hours, pickling them slightly. It may also be called namasu-kiri ( kiri means "sliced").