This is the 15897th most frequent Russian word.
пропускать
To miss, skip, or let pass.
In this sentence, 'пропускать' means 'to skip' and is used to express the action of missing classes intentionally.
Она решила пропускать занятия задолго до экзаменов.
She decided to skip classes well before exams.
Here, 'пропускать' is used in the sense of 'to miss' and implies neglecting to take advantage of an opportunity offered.
Пропускать такую возможность было бы глупо.
It would be foolish to miss such an opportunity.
In this instance, 'пропускать' means 'to let through' and describes the action of allowing the water to pass through the filter.