This is the 13692nd most frequent Russian word.
неофициальным
"Unofficial."
The word 'неофициальным' here is used to describe the nature of the dinner, indicating that it was not formal or ceremonial.
Этот ужин был весьма неофициальным мероприятием.
This dinner was quite an informal event.
In this sentence, 'неофициальный' is employed to describe the style of communication, emphasizing a casual manner.
Он всегда предпочитает неофициальный стиль общения.
He always prefers an informal style of communication.
Here, 'неофициальной' characterizes the setting as lacking formalities, suitable for preliminary or casual discussions.