Fluttering pitch

• Pitcher's specialty
• Tricky delivery
• Tough-to-hit pitch
• Pitcher's choice
• Certain slow pitch
• Unpredictable pitch

Wikipedia Word definitions in Wikipedia
A knuckleball or knuckler is a baseball pitch thrown so as to minimize the spin of the ball in flight, causing an erratic, unpredictable motion. The air flow over a seam of the ball causes the ball to transition from laminar to turbulent flow. This transition ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
also knuckle-ball , baseball pitch, by 1909, from knuckle (n.) + ball (n.1). So called from the position of the fingers in throwing it. Related: Knuckleballer .

WordNet Word definitions in WordNet
n. a baseball pitch thrown with little speed or spin [syn: knuckler ]