Fastball rhymes with:
basketball, football, meatball, racquetball, softball, spitball, arenaball, basketball, blackball, butterball, cannonball, eyeball, fireball, football, handball, hardball, meatball, mothball, oddball, pinball, powerball, racquetball, screwball, snowball, softball, spaceball, spitball, stickball, tidball, trackball, volleyball