Use a damn dictionary.
in·sur·gent Audio pronunciation of "insurgent" ( P ) Pronunciation Key (n-sûrjnt)
adj.
1. Rising in revolt against established authority, especially a government.
2. Rebelling against the leadership of a political party.
ter·ror·ist Audio pronunciation of "terrorist" ( P ) Pronunciation Key (trr-st)
n.
One that engages in acts or an act of terrorism.
ter·ror·ism Audio pronunciation of "terrorism" ( P ) Pronunciation Key (tr-rzm)
n.
The unlawful use or threatened use of force or violence by a person or an organized group against people or property with the intention of intimidating or coercing societies or governments, often for ideological or political reasons.
Edit: If you dislike them and their cause, they are terrorists. If you do like them or their cause, or don't care one way or another, they are insurgents.