adjective/bœ.ʁe kɔm œ̃ p(ə).ti ly/
pissed as a newt; drunk as a skunk (very drunk)
Synonyms: plein comme un œuf, bourré comme un coing
Literally, “buttered as a Petit LU”, a type of shortbread (biscuit with a high concentration of butter) manufactured by "Lefèvre-Utile". A pun, beurré meaning both "drunk" and "buttered".