What is race condition?

A race condition is a situation in which a computer system tries to process at least two operations simultaneously,
http://www.wisegeek.com/what-is-a-race-condition.htm

a situation in which multiple processes read and write a shared data item and the final result depends on the relative timing of their execution
http://wiki.answers.com/Q/What_is_race_condition_in_operating_systems

The race condition is the situation where several processes access and manipulate shared data concurrently. The final value of the shared data depends upon which process finishes last. To prevent race conditions, concurrent processes must be synchronized.
http://www.basicsofcomputer.com/race_conditions_in_operating_system.htm

A race condition occurs when 2 or more threads are able to access shared data and they try to change it at the same time
http://stackoverflow.com/questions/34510/what-is-a-race-condition