What does the idiom sharp as attack mean?

The idiom "sharp as a tack" is the correct phrase, not "sharp as attack." It means very intelligent, quick-witted, and alert.

Here are some examples of how to use it:

* "My grandmother is 80 years old, but she's still as sharp as a tack."

* "The new intern is incredibly sharp as a tack - he's already learned so much."

* "The lawyer was sharp as a tack and quickly saw through the defendant's alibi."

The idiom originates from the image of a tack, a small nail with a sharp point, being able to pierce through something easily.