This is the 17733rd most frequent Russian word.
ужином
"Uжином" means "dinner" or "supper" in the instrumental case in Russian.
In this sentence, "ужином" is the instrumental case of the noun "ужин," denoting the means or association during the activity (means through or with which the activity of enjoying took place).
Мы наслаждались приятным ужином в ресторане.
We enjoyed a lovely dinner at the restaurant.
Here, "ужином" in the instrumental case indicates the environment in which the action occurred (setting or surroundings for sharing thoughts).
Она делилась своими мыслями за ужином.
She shared her thoughts during dinner.
Although "ужином" itself isn't visibly instrumental in this example, the phrase "накануне ужина" implies temporal context, designating the time associated closely with "ужин."