I’ll bite:

A wrecker is a person who stirs shit in a community in a negative manner. This can be intentional or unintentional, but it doesn’t matter, the result is the same. Wreckers “wreck” a community.

In a way, it’s similar to calling someone a “fed,” but the implications are a bit different. Whereas a fed is either an employee of a nation-state intelligence agency or a paid informant, wreckers could be doing fed shit for free, and even unintentionally.

There is a long and storied history of wreckers destroying left wing groups and movements. I am personally aware of two local left wing groups that were dismantled by a very small number of wreckers, and it has taken us years of hard work to rebuild them from the ground up when the wreckers could have left if they were honest or been kicked out and the work continued. Now, these people may have just been assholes, but the effect was the same: a suppression of left wing activism in my local community and wins for capital.

People often misappropriate Marxist, anarchist, or even therapeutic terminology and language in a way that is intellectually dishonest and results in infighting that pushes activists and potential activists away or results in the dissolution of the group entirely. Whether this is intentional or not is unimportant: the result wrecks movements and is wrecker behavior.