A BUNT is a batted ball not swung at, but intentionally met with the bat and tapped slowly within the infield.
Holding the bat in the strike zone does not constitute a strike at the ball. In this video the batter holds bat in the strike zone. No strike.http://mlb.mlb.com/video/play.jsp?content_id=19955313
If the batter intends to meet the ball with the bat and misses, it is a strike.
It is not a bunt if the bat is pulled back in an attempt to not intentionally meet the ball. In this video the batter pulls his bat back, but the ball is fouled. The umpire crew determines that the batter did not intentionally meet the ball with the bat, therefore the ball was is treated as a foul ball, and not a bunted foul for a third strike out (see Rule 6.05(d))
When a batter starts running before bunting the ball, it is known as a "drag bunt."
Rule 2.00 INFIELD FLY
Rule 2.00 SQUEEZE PLAY
Rule 2.00 STRIKE