noun
onion soup au gratin; French onion soup
A Japanese wasei-eigo term for a dish of onion soup topped with bread and cheese, then baked or broiled until the cheese melts and browns. Essentially the same as French onion soup served au gratin style.
wasei-eigo (Japanese-coined English), from onion gratin
寒い日にはオニオングラタンが食べたくなる。
On a cold day, I crave onion soup au gratin.
この店のオニオングラタンはチーズがたっぷりで
The onion soup au gratin at this restaurant is delicious with plenty of cheese.