expression, noun
eating a lot, drinking a lot, and on top of that, eating mochi
A humorous or exaggerated set phrase describing someone who eats and drinks heavily and still manages to eat mochi. Rare and idiomatic; not used in everyday conversation.
彼は大食上戸餅食らいで、宴会ではいつも最後まで食べている。
He's a big eater and drinker who even manages to eat mochi on top of that, and at banquets he's always eating until the very end.
A compound of 大食 (big eating), 上戸 (heavy drinker), and 餅食らい (mochi eater). The exact origin is uncertain; it appears to be a playful, idiomatic listing of indulgent behaviors.