The finer point is, I think, that they did not get they power legally in the elections, because no such power can be granted in elections. Elections are a way to elect the national assembly which can then create a government, write laws etc.; but things that happened after 1946 and especially after 1948 were not supported by legal power, but by Stalin's terror and totalitarian dictature.
Its true that in 1948 the elections were a sham since there was only a single party to vote for - communist one, hence their total victory in both Czech and Slovak part of the republic. But the true rise to power was in 1946 that enabled all that came later, and was done via those democratic elections.
Coup d'etat sounds like there was a democratic government overthrown by some communist fringe movement outside government, which isn't true. They got to power and got majority, and used it to remove everybody else. Maybe my idea of coup d'etat is incorrect and this whole discussion is kind of pointless.