Definition: Moving away and often down from.
Like "on", this sign is not that much commonly used, if not rarely, since most signs have their own integrated verb phrases that don't separate a verb from a preposition (e.g. off).
This fingerspelled loan is also commonly used in some contexts, such as TURN+#OFF, LIGHT+#OFF, etc. but you cannot use it in "pay off" (or such) because it has its own single sign.