Denial of Service (DoS)

The prevention of authorized access to resources or the delaying of time-critical operations. (Time-critical may be milliseconds or it may be hours, depending upon the service provided). 
 
See the following for more information: 

NIST SP 800-12 Rev. 1 under Denial of Service. 

NIST SP 800-33 and NISTIR 7711 under Denial of Service.
NIST SP 800-27 Rev. A.

The prevention of authorized access to a system resource or the delaying of system operations and functions. 

See NIST SP 800-82 Rev. 2 under Denial of Service (DoS) for more information. 
 
Actions that prevent the NE from functioning in accordance with its intended purpose. A piece of equipment or entity may be rendered inoperable or forced to operate in a degraded state; operations that depend on timeliness may be delayed. 
 
See NIST SP 800-13 under Denial of service for more information.