Green’s Dictionary of Slang

1. to show off, esp. by parading oneself in front of an audience.

1957		‘Ed Lacy’ Lead With Your Left (1958) 38: Seems you don’t have enough work, you have time to showboat.
1967		M. Braly On the Yard (2002) 70: The need for recognition grew like hunger. In time he would showboat and the captain would hear about it.
1975		E. Torres Carlito’s Way 136: The dude was hurt bad [...] but he showboated his way out like ’tweren’t nothin’.
1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 23: Carol, show-boating her irritation, gave a rebuke.
2005		P. Howard Curious Incident of the Dog in the Nightdress 99: I told the guys not to be afraid to showboat a bit in the second half.
2010		A. Steinberg Running the Books 266: He was slick and successful [...] showboating at the swanky Sugar Shack club.
2015		L. McInerney Glorious Heresies 3: [N]ow that everything had changed he couldn’t remember how to showboat.
2024		J. Meades Empty Wigs (t/s) 292: [N]o one showboats or we all showboat and I showboat most of all.

2. to show someone or something off, to display, to parade.

1969		Time 31 Jan. 59: The 98-year-old ballet is traditionally noted for [...] the opportunity it affords a ballerina to showboat her versatility.
1988		H. Gould Double Bang 142: You think I’m showboatin’ you?
1994		N. McCall Makes Me Wanna Holler (1995) 289: He grabbed the winner’s hand and thrust it skyward, like a referee showboating a prizefighter.