Everyone who uses the Internet knows what Wikipedia is. But what's that other word that often comes up in the same context? "Wikimedia"?
The term is actually a retronym, coined in 2003 when the WMF was established. Wiktionary had been created in 2002 and other projects followed soon, so the new word allowed for greater flexibility and distinction.
That said, it's kind of a chore to explain to outsiders. As a result, the word tends to be used interchangeably even inside the movement. See for example: Wikipedians-in-residence, who may work more often with Wikimedia Commons.
As a mnemonic, you might think of the "m" in "Wikimedia" as standing for the movement. Wikipedia, though, is all about the 'pedia.