Did the British government officially call American revolutionaries "terrorists" or any acts of theirs "terrorism"?
If they did, was it justified under modern common-denominator definition of terrorism (namely, intentional attacks on civilians, with the goal of political change)?
Under this definition, guerilla warfare against military forces do NOT get included.
Terrorism - the word
It is impossible for the British Government to have called the revolutionaries 'terrorists' during the Revolutionary War. The word was not coined until late in that century, and was then applied only to the Reign of Terror of the French Revolution. The word did not acquire its modern usage until just after World War 2, when it was used to refer to Zionist revolutionaries in Israel.
The British did refer to the Patriots at the time as rebels and traitors and deviants.
The definition of terrorism used in the question - "intentional attacks on civilians, with the goal of political change" is quite wide ranging, and could include a number of acts we might not usually think of as terrorism. However if we accept it, it is very clear that terrorist acts were committed during the Revolutionary War by both sides. Despite Hollywood's portrayal of the Revolutionary War as a fight between Yankee-accented farmers and British-accented overseers, the Revolutionary War was in essence a civil war; Loyalists and Patriots looked the same, spoke the same and often came from the same families. The same was true of the 'British' soldiers, who were often recruited in the Colonies, and might find themselves firing at - and being fired on by - their friends, neighbours and family. The only difference between a Loyalist and a Patriot was their politics.
It is absolutely certain that there were attacks on civilians by both sides of the conflict. Houses of Loyalists were frequently set on fire, and their property confiscated (see here, here, here, here and here, as well as many others). Tar-and-feathering of those who opposed your cause - or sometimes simply didn't support it enough - was also commonly used by both sides. The Boston Tea Party was certainly targeted at civilians with the goal of political change. Loyalists in return burned and looted the houses of Patriots where they were in the majority.
The final part of the question: I've been unable to find any cases of the British Government officially calling the American Revolutionaries "terrorists" since the word acquired its modern usage, and it would be a very unlikely thing for them to do, given the relations between the countries since then.
Aside from the fact that the term 'terrorism' as we understand it today didn't exist in the mid 1700's, the British would have to account for their own participation in what might be regarded to be terrorist activities during that war.
Notably, the actions of Banastre Tarleton, especially in the southern campaigns, where his troops destroyed farms and other agricultural infrastructure as part of their effort to frighten the local residents into submission. That policy would be regarded as a terrorist campaign today. Ironically, US General Sherman did exactly the same thing, in the same locale (Georgia), almost 100 years later.
Applying contemporary judgments to actions that occurred in the past, when societies were quite different, can lead to false conclusions.