In professional wrestling, a bump occurs whenever a wrestler hits the mat or the arena floor after receiving a move from his/her opponent. It can also refer to hitting the floor as a result of a missed aerial move. Every wrestler is trained to take bumps while avoiding injury, though they are not always successful in emerging unhurt. Some wrestlers are more willing to take bumps than others, and some even base their entire careers on taking massive bumps.
While there are innumerable ways to take bumps, there are two basic varieties. The schoolboy bump is one in which a wrestler falls backwards, kicking up his feet and landing on his back. It is so named because it is the result of a schoolboy trip maneuver. A schoolboy bump in which the wrestler jumps into the air before falling backwards, as when being chokeslammed, is called a high schoolboy. The Biel bump is one in which a wrestler falls forwards, rolling forwards or performing a forward flip before landing on his back. It is named after the Biel throw. Other kinds of bumps are usually variations on these.
A ref bump occurs when a wrestler collides with or otherwise attacks (whether intentionally or not) a referee. This usually results in the referee being "knocked out" or incapacitated for a time, allowing one or more wrestlers (normally the heel) to break the rules with impunity until the referee comes to or another referee is sent out to replace him. Ref bumps are an essential part of a successful Dusty finish.
To emphasize the power and fortitude of the wrestlers, referees are frequently knocked "unconscious" for long periods of time by moves that would not be considered particularly devastating when applied to wrestlers. For example, a wrestler being Irish whipped by his opponent may clip the referee. While a wrestler would probably only be knocked back in this situation, the referee would most likely be knocked across the ring and act injured or knocked out. This is referenced in multiple variations in WWE SmackDown! vs. RAW 2006 when a ref bump occurs, such as announcer Tazz's remark about the WWE needing "sturdier refs". Other performers can take bumps as well, including managers, valets/divas and others who are either participating or not participating in a match.
And how does taking a chair shot, make you master of bumps?