Green’s Dictionary of Slang

1. (US) amateur, unprofessional, unsophisticated; thus bushleaguer n., a person who is a failure.

[1902		Lincoln (NE) Eve. News 21 Feb. 4/6: Sioux City will belong to the north tri-state league, composed of Rock Rapids, Sheldon, Le Mars, Iowa, Flandreau, Yankton and Sioux Falls, S. D., generally known as the ‘bush league.’].
[1908		N.Y. Globe 20 Mar. in Fleming Unforgettable Season (1981) 30: The Giants [...] quit the bush league circuit after one day’s experience].
1912		Van Loan ‘The Phantom League’ in Ten-Thousand-Dollar Arm 180: Huh! [...] some bush-league newspaper man trying to be funny.
1920		Ade Hand-made Fables 7: When the beaded Bubbles were bursting at the Brim, then Billy’s Bush-League Wheezes would set the whole Table cackling.
1935		C. Odets Awake and Sing! II i: Don’t be a bush leaguer all your life.
1944		C.B. Davis Rebellion of Leo McGuire (1953) 69: You come with me, Leo, and you won’t be a bushleaguer.
1949		A. Hynd We Are the Public Enemies 46: In March of 1930, two young bush league robbers [...] broke out of separate Texas jails within three days of each other.
1959		W. Burroughs Naked Lunch (1968) 16: Some bush league short con artist.
1966		H.S. Thompson Hell’s Angels (1967) 44: Until the Monterey rape they were bush-league hoods known only to California cops.
1977		(con. 1949) J.G. Dunne True Confessions (1979) 94: He was strictly bush league, Turd. He couldn’t even stick up a candy store without fucking up.
1983		R. Price Breaks 195: My second effort, a bush-league parody of greed on game shows.
1990		R. Malan My Traitor’s Heart (1991) 167: A sort of bush-league Rolling Stone called Vula.
2001		J. Stahl Plainclothes Naked (2002) 49: It’d look bush-league for a cop to give ’em a tip and have somebody else arrest the guy.
2018		‘Aidan Truhen’ Price You Pay 178: Hi Karenina are we not friends any more? Price this is fucking bush league.

2. (US campus) unfair, stupid, inadequate.

1989

P. Munro Sl. U. 50: I didn’t get housing. — That’s bush-league.