Wiktionary
n. A short flounced skirt of a style similar to that worn by cheerleaders.
Wikipedia
The rah-rah (or ra-ra) skirt is a short flounced layered skirt that originated in cheerleading and became a popular fashion trend among teenage girls in the early 1980s. As such it marked, as the Oxford Dictionary noted, the first successful attempt to revive the miniskirt that had been introduced in the mid-1960s. Later in the 1980s it was often worn with leather, denim or lace.
In the 1990s the mini came back into fashion in its own right, largely discarding the frills of the rah-rah. However, the latter did return again in Britain in 2008: "Eighties look is all the ra-rave".
Examples of the rah-rah were to be seen on the covers of gramophone records or compact discs such as Since Yesterday by Strawberry Switchblade (1984).