be on the ball

• Быть внимательным, быстро понимать и эффективно действовать или мыслить; быть высококомпетентным и быстро реагировать в данной ситуации.

To be alert, quick to understand, and efficient in one's actions or thinking; to be highly competent and responsive in a given situation.

1. Alert and quick to understandB2informal

   To be alert, attentive, and quick to understand or react to a situation.

   Быть начеку

   • You need to be on the ball during the exam to finish on time.
   • The new assistant is really on the ball; she caught the error immediately.
   • To succeed in this job, you have to be on the ball at all times.