1. noun
a) A person, group, or organization that uses violent action, or the threat of violent action, to further political goals; frequently in an attempt to coerce either a more powerful opponent, (such as a citizen or group targeting a government), or conversely, a weaker opponent, (such as a government, or even an internal citizen or group, being targeted by a larger government).
b) An agent or partisan of the revolutionary tribunal during the in France.
2. adjective
Of or relating to terrorism.
Wikipedia foundation.