Hey, my friend and I are helping out our HS basketball team by keeping the stats. We're a little clueless when it comes to turnovers. so . . . What's the official definition of a Turnover and is there a special hand singal that the ref will make when one occurs??? Thanx

No, there isn't a hand signal for a turnover. If you're team has the ball and loses it by committing a floor violation or a foul, the dfense steals the ball, you're team has committed a turonover. Floor violations include traveling, 3 secs., 5 seconds closely guarded or on a throw-in, a backcourt violation, or simply losing the ball OOB. A player control foul or a foul for an illegal screen are examples of fouls that would result in a turnover.

also
 

if the team loses the ball when the whistle is not blown like bad passes to opponents, dribbling off their foot, and other general screw-ups.

When you have the ball, you either get a shot or you turn it over (and for you nitpickers out there, the period can also end without shot or turnover!). If you rebound your missed shot, you again have possession and you either shoot the ball or turn it over. If the defense gets the ball through anything other than a rebound, the offense turned it over.

Coach,
That's pretty clean.
mick