This is the 3108th most frequent Portuguese word.
barrar
To block, bar, or prevent.
In this sentence, 'barrar' is used to mean 'to block' or 'prevent access to' something, in this case, the club's membership.
Eles decidiram barrar a entrada de novos membros no clube.
They decided to block the entrance of new members to the club.
Here, 'barrar' is utilized to signify 'to halt' or 'stop something in its progression or advance, applied to an abstract concept like a disease.
Ela conseguiu barrar o avanço da doença com o tratamento adequado.
She managed to halt the progression of the disease with appropriate treatment.
In this example, 'barrar' denotes 'to bar' or temporarily prevent a process or action like the implementation of a law.