These are the three definitions of terrorism at dictionary.com.
1. the use of violence and threats to intimidate or coerce, especially for political purposes.
2.the state of fear and submission produced by terrorism or terrorization.
3.a terroristic method of governing or of resisting a government.
The definition of a terrorist at the same website is.
1.a person, usually a member of a group, who uses or advocates terrorism.
2.a person who terrorizes or frightens others.
Official United States Government Definition of Terrorism states (B) appears to be intended (i) to intimidate or coerce a civilian population.
Thus by the governments own definition of terrorism, police officers are terrorist. Are you more afraid of police officers or Al Qaeda?