Rushdown is the art of putting pressure on the opponent by running them down with moves (or strings) that don’t have much opening such that it becomes difficult for them to take any action.
The Japanese call this katame, meaning “hardening” (because you force the opponent to lock up if you’re doing it right). The word “rush” could imply that it’s done all at once, trying to elicit a panicking mistake, but in truth, rushdown/katame can be as cold and fearsomely slow (but just as calculating) as well as fast and alarming.
This is the offensive counterpart to the defensive turtling strategy; it can hardly be considered the act of a chicken, but taken to an extreme, it may actually be cheap at times.