To me, the term bush league stands for dirty plays and dirty players. I suppose there is a fine line sometimes between hard-nosed plays and cheap-shot or bush league plays. I considered Pedro Martinez to be a bush league player. Get a hit off him and you were almost guaranteed to get hit in the middle of the back with a 95 mph fastball the next time up. If a fight ensued because of his antics, Pedro was always the first one to be hiding in the dugout - unless of course 90 year old Don Zimmer was the opponent and then Pedro had the courage to stand up for himself.
A play that was controversial and could be argued both ways was Pete Rose bowling over Ray Fosse in the All-Star game. I never heard anyone call it bush league but it was debatable whether that tactic was necessary in an exhibition game. Of course, Rose only knew one speed so he didn't suffer any serious repercussions from the incident.
I really never considered trick plays or deceptive plays to be bush league. A-Rod's play although perhaps embarassing to A-Rod in the way he slapped at the ball never seemd like a bush league play to me.