To me, it depends on the context. However, I understand these following things: 1) The cheater (somebody who doesn't do a challenging objective the way that it's supposed to be done) is cheated on. For example, the cheater was cheating on a math test. However, some other cheater cheated off of the first cheater's math test. 2) The cheater (somebody who betrays a significant other by having romantic relations with a 3rd party) got cheated on. For example, a cheater is also someone who betrays their significant other to have romantic relations with a 3rd party (another person.) The same significant other that the first cheater cheated on, cheated on the first cheater (by having a romantic relationship with a different third party.) Therefore, people will interpret this context as a couple who cheated on each other with different people. ------------------------------------------------------------------------------------------------------------- In conclusion, this sentence really depends on the context because it can many different meanings. The best way to know what somebody is trying to communicate is from the context. If somebody is talking about academics, then cheating will probably mean finishing a task the way it was not intended. However, if we're talking about romance, cheating probably means betraying a significant other.