This is the 15756th most frequent Russian word.
пробный
"Trial" or "test".
Here, 'пробный' refers to a version or instance of something intended for testing purposes before full implementation or use.
Мы приобрели пробный экземпляр новой программы.
We acquired a trial copy of the new program.
In this context, 'пробный' modifies 'тест', meaning a preliminary or practice test used for preparation or evaluation ahead of the actual one.
На курсе мы сделали пробный тест.
In the course, we took a trial test.
Here, 'пробный' describes the initiation or operation of equipment aimed at verifying functionality before regular use.