insurgent

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Rising in revolt against established authority, especially a government.
2. adj. Rebelling against the leadership of a political party.
3. n. One who is insurgent.

Century Dictionary and Cyclopedia

1. Rising against lawful authority or established government; engaged in insurrection or rebellion: as, insurgent chiefs.
2. n. One who rises in forcible opposition to lawful authority; one who engages in armed resistance to a government or to the execution of laws.
3. n. Synonyms Insurgent, Rebel, Traitor. An insurgent differs from a rebel chiefly in degree. The insurgent opposes the execution of a particular law or scheme of laws, or the carrying out of some particular measure, or he wishes to make a demonstration in favor of some measure or to express discontent; the rebel attempts to overthrow or change the government, or he revolts and attempts to place his country under another jurisdiction. A traitor is one who breaks faith or trust by betraying his country or violating his allegiance, especially a sworn allegiance: the word is applied in strong reprobation to one who, even without express breach of faith, makes war upon his sovereign or country, or goes over from the side to which his loyalty is due. See insurrection.

Wiktionary

1. adj. Rebellious, opposing authority.
2. n. A rebel, guerrilla, freedom fighter.

GNU Webster's 1913

1. adj. Rising in opposition to civil or political authority, or against an established government; insubordinate; rebellious.
2. n. A person who rises in revolt against civil authority or an established government; one who openly and actively resists the execution of laws; a rebel.

WordNet 3.0

1. n. a person who takes part in an armed rebellion against the constituted authority (especially in the hope of improving conditions)
2. adj. in opposition to a civil authority or government
3. n. a member of an irregular armed force that fights a stronger force by sabotage and harassment