I was just musing on this because the British PM said that the murderous machete assault on a British soldier outside his barracks in London might be "an act of terror."
This follows on the ridiculous political theater in the US over when President Obama said the Benghazi attack was "an act of terror" and whether he lied about when he said it.
Because the Benghazi attack was not terrorism at all, and neither was the London attack. Terrorism is a word with a meaning. It means attacking civilians as a way to spread fear and thereby accomplish some political goal.
In Benghazi, members of a radical Islamic militia attacked a heavily armed CIA compound. They had no interest in killing civilians; they wanted to kill CIA agents. That's not terrorism, that's war. I suppose what PM Cameron meant was that the machete attack was intended as a political act, but that doesn't make it terrorism. Terrorism means attacking civilians, not soldiers.
We have turned the meaning of this word into a political symbol. If you call every sort of attack on Western interests "terrorism," that somehow means you are standing tough against Islamic extremists. Really it just means you don't know English very well.