When it comes to the ball Eliot is the man. cowboy...

play catch (with a ball) = go outside and throw to ball to one another and catch it Playing catch with the conversation ball is just another of those crazy ESL ideas to help students of English have fun in class (instead of actually learning some English).

its is just someone want to play, then he gave the ball to someone so they want to started to play the game.

Agree with Eliot. It seems to be a game where one player says a word (e.g. in native language) and throws a ball to another player. The latter is to give the right answer (e.g. translation in English) in response and to throw the ball back.

sounds like lets have a chat