In poker, collusion is any action where two or more players work together to gain an unfair advantage over their opponents. It occurs both in live and online poker and is considered cheating.
There are many ways in which poker players can collude. Online, for example, two players could share their hole cards, which can give them a decisive edge in certain spots. They could also work together to bet and raise until they push other players out of the pot, securing that one of them will win the hand. Players can also participate in chip dumping to move chips around to the player that needs them the most.
RTA and ghosting are additional forms of cheating.
In all its forms and instances, collusion falls under cheating, and it is frowned upon by players, cardrooms, and online poker operators alike. Players caught colluding can face serious consequences, including legal action.