Wiktionary
n. The use and management of information in pursuit of an advantage over an opponent, such as propaganda, disinformation, and gathering assurances that one's own information is accurate.
WordNet
n. the use of information or information technology during a time of crisis or conflict to achieve or promote specific objectives over a specific adversary or adversaries; "not everyone agrees that information warfare is limited to the realm of traditional warfare" [syn: IW]
Wikipedia
Information warfare (IW) is a concept involving the use and management of information and communication technology in pursuit of a competitive advantage over an opponent. Information warfare may involve collection of tactical information, assurance(s) that one's own information is valid, spreading of propaganda or disinformation to demoralize or manipulate the enemy and the public, undermining the quality of opposing force information and denial of information-collection opportunities to opposing forces. Information warfare is closely linked to psychological warfare.
The United States military focus tends to favor technology, and hence tends to extend into the realms of electronic warfare, cyberwarfare, information assurance and computer network operations, attack and defense.
Most of the rest of the world use the much broader term of "Information Operations" which, although making use of technology, focuses on the more human-related aspects of information use, including (amongst many others) social network analysis, decision analysis and the human aspects of command and control.