Today’s definition of multicloud depends on who you ask. This is not a new trend. Whenever a new technology gets some hype, suddenly there is semantic confusion.
My definition is a bit more holistic than most: Multicloud is a collection of public clouds, private clouds, and legacy systems (yes, I went there). Two or more public or private clouds must be present to be true multicloud. Legacy systems are optional but also good to include.
A charted representation of my definition looks like this: