Movies that, while there are certainly
many females that enjoy them, are
generally enjoyed more by
males and are therefore usually more fun to watch in the company of other males. Oftentimes, these movies contain lots of
explosions,
car chases,
special effects, gratuitous
sex and sex-related content, etc.
Contrary to popular belief, guy movies are not always bad movies. Examples of good movies that are also guy movies: anything with Sean Connery in it, Aliens, Star Wars, Star Trek 2, 4, and 6, etc.
This, of course, assumes that the reader acknowledges the difference between a movie's quality and enjoyability. While the two often go together, one does not imply the other.