Definition from Wiktionary, the free dictionary
sis boom bah
- an exclamation of encouragement
- The term is popular in U.S. high school and college cheers.
- It has also been used by Bugs Bunny in the iconic cartoon, "Super-Rabbit"
- Bugs: Bricka bracka fia cracka sis boom bah! Bugs Bunny! Bugs Bunny! RAH! RAH! RAH!
- (dated) The characteristic sound made by a firecracker.
- Often proceeded or succeeded by rah rah