Terrorist attack and Terrorist act

Terrorist attack noun - A surprise attack involving the deliberate use of violence against civilians in the hope of attaining political or religious aims.

Terrorist act and terrorist attack are semantically related. In some cases you can use "Terrorist act" instead a noun phrase "Terrorist attack".

Terrorist act noun - The calculated use of violence (or the threat of violence) against civilians in order to attain goals that are political or religious or ideological in nature; this is done through intimidation or coercion or instilling fear.

Terrorist attack and terrorist act are semantically related. Sometimes you can replace phrase "Terrorist attack" with "Terrorist act", this phrases are similar.