a person who displays conspicuous diligence, esp one who volunteers for extra work
eager beaver in American English
US
Slang
a person characterized by much, or too much, industry, initiative, or enthusiasm
eager beaver in American English
(ˈiɡər)
noun
a person who is excessively diligent or overly zealous
Word origin
[1940–45, Amer.]This word is first recorded in the period 1940–45. Other words that entered Englishat around the same time include: Rh factor, black box, blockbuster, update, zap