The weak man fallacy occurs when an arguer treats some weaker arguments for a position as encompassing the overall argument for that position, conveniently ignoring stronger arguments that exist for the same position.

Here is an example:

"Those who oppose international treaties to mitigate climate change include people who believe the whole world will end five years from now when space aliens come and destroy Earth so that there is no point in worrying about climate change. Such is the insanity of this position."

There may be people who believe that, but not everyone showing reluctance about such treaties believes any such thing. There are stronger arguments that should be examined, instead of pretending that the weakness of the "space aliens" argument is indicative of all of them.

Because it misrepresents the true range of arguments of the opposing side, weak man is considered to be a specific type of straw man fallacy.

Note that a common tactic with this fallacy is to combine it with nut-picking, whereby the arguer selectively mentions some of the most extreme or exaggerated arguments for a position, and uses them to represent the entire range of arguments for that position.