Definition from Wiktionary, the free dictionary
- (idiomatic) Someone who is very busy or hard-working.
- Wow! Laundry, dishes, and errands, all in one day? You've been a busy beaver.
- (computing theory) A Turing machine that attains the maximum number of steps performed, or number of non-blank symbols finally on the tape, among all Turing machines in a certain class.