Hands that are larger than normal. More specifically, the hands tend to be as big as the head, or slightly bigger. This does not take into account Perspective or Foreshortening.
Having hands larger than normal is generally considered to be a masculine trait that some find attractive, so much so it has become a trope in the Yaoi genre, often called "Yaoi hands". However, large hands can be a character design choice as well, especially as a way to imply that the character isn't completely "human". Since this design choice is not very common, the hand sizes for such characters tend to be more variable, especially in fan art.
Not to be confused with Oversized Forearms.