A “straw man” argument is an argument that in intends to present either a weak or erroneous aspect of an opposing view, in order that by its easy defeat, the competing view appears stronger than it really is.
Again, the reality, though, is that most often Calvinists allege a “straw man” argument as a hand-waving tool, in order to try and save face, and thus escape from having to provide a meaningful defense.