I have always thought that a counter attack meant an attack that Player A does as Player B is doing a big push. In other words, a counter attack by definition can only exist as a response to an attack.
However, I have seen a lot of casters (including day) use the term counter attack as a synonym for speedlings harassing mineral lines, regardless of whether the non zerg is attacking. Is this just a misunderstanding on my part, or has "counter attack" become equivalent to "harassment"? If so I pine for the days of more precise language.