Definify.com
Webster 1913 Edition
Boomer
Boom′er
,Noun.
1.
One who, or that which, booms.
2.
(Zool.)
A North American rodent, so named because it is said to make a booming noise. See
Sewellel
. 3.
(Zool.)
A large male kangaroo.
4.
One who works up a “boom”.
[Slang, U. S.]