Tapping one's fingers is a common gesture used to express impatience or frustration. It is often done in a rhythmic pattern, similar to drumming, which is why the crossword solution for this term is 'DRUM'. This gesture is usually done with the index and middle fingers of one hand, and can be done on any surface, such as a table or desk. Tapping one's fingers is a way to show that someone is feeling restless or bored, and is often done when someone is waiting for something to happen.