This is the 16133rd most frequent Russian word.
разовой
"Разовой" means "one-time" or "single-use."
The word 'разовая' here describes the assistance as being provided one time, not recurring.
Разовая помощь была очень полезной.
A one-time assistance was very helpful.
'Разовая' is used to describe the opportunity as unique and not to be repeated.
У нас есть разовая возможность посетить это место.
We have a one-time opportunity to visit this place.
In this context, 'разовой' indicates that the deal is occurring only once.