A fungo bat is specially designed bat used by baseball and softball coaches for practice purposes. The bat is not designed to hit thrown or pitched balls, rather it is designed to hit balls tossed up in the air. Typical fungo bats are 35–37 inches long and weigh 17–22 ounces. Coaches hit many balls during fielding practice and the weight and length allow for the coach to hit balls repeatedly with high accuracy.
From the article on Bats