A smasher is somebody who plays a Super Smash Bros. game, usually Melee. Although even casual Smash Bros. players can be considered smashers, the term is mostly used in the Smash community when talking about competitive players and professionals, especially those who compete in local or regional tournaments.
Competitive scene
Many smashers have earned recognition by participating in (or hosting) unofficial tournaments, mainly for Melee. These tournaments have allowed smashers around the world to connect with others and make a name for themselves in the Smash community, as well as test their skills and possibly earn prizes.
Skill levels
A smasher can range from any skill level, from a novice player who is just starting out to a top professional. In the competitive Smash scene, several different skill levels can be used to define a smasher; the most common of these are Amateur, Professional Amateur (pro-am), Professional, and Top Professional. The only official level higher than Top Professional is World Champion, the best Super Smash Bros. (or Melee) player in the world, according to tournament statistics. The current World Champion is Ken Hoang.
An "amateur" Smasher is one who is not affiliated with any professional gaming league, whereas a "professional" Smasher is one who has been recruited by a notable professional organization, such as MLG. A "professional-amateur" Smasher is an amateur Smasher who is widely recognized as being able to compete on an even level with the professionals.