In the ScrumProcess, this is the person responsible for keeping the team following the process. This is somewhat similar to a ProjectManager role. However, because Scrum asks the team to organize itself, this person may or may not be the perceived "leader" in a given Sprint.
The ScrumMaster is the team member responsible to interface with the world outside the ScrumSprint, and to remove/resolve blockages that impede the team's work within the ScrumSprint.
Also, term used for a graduate of the ScrumMasterCertification program.
-- DebHartmann
See also: CertifiedScrumMaster