champ at the bit (US ALSO chomp at the bit)
to be eager and not willing to wait to do something

[TahlilGaran] Advanced Learner's Dictionary ▲

champ at the bit
to be very eager.
The phone companies are champing at the bit to expand into these new lines of business.

Etymology: based on the idea of a horse chewing on the bit (= piece of metal in its mouth that allows a rider to control its movements) when excited or nervous

[TahlilGaran] English Idioms Dictionary ▲

champ at the bit
• champ/chomp at the bit
to be ready and anxious to do something (a bit is put into a horse's mouth for control of the horse)
Everybody was champing at the bit to start writing the test.

Everyone was chomping at the bit to get started on their holiday.

[TahlilGaran] English Idioms Dictionary ▲

champ at the bit
v. phr. To be eager to begin; be tired of being held back; want to start.
The horses were champing at the bit, anxious to start racing.
As punishment John was kept after school for two hours. He was champing at the bit to go out.

[TahlilGaran] English Idioms Dictionary ▲