Meaning

noun an informal form of address for a man

noun a robust child

noun a person who breaks horses

originOriginally a dialectal variant of burster; later influenced by bust + -er. The combining form of the term has appeared from the early 20th century but been especially prolific during three periods: in the 1930s, owing to the success of the radio series Gang Busters; in the 1940s, owing to its appearance as military slang; and in the 1980s, owing to the success of the movie Ghostbusters.

Etymology from Wiktionary, CC BY-SA 3.0