Actually, no, it's exactly the functionally descriptive term I'm challenging.
The normal definition is a memory with flat access times - i.e. it doesn't matter what part of the memory you access, you can do it equally quickly. This doesn't apply for things like tapes or HDDs, which are respectively either sequential or semi-sequential (sequential per cylinder) access.
In the case of flash the time to perform a write is strongly dependent on the preexisting erase state of the block - if it's cleared already, it's much faster than if you need to clear it. That means that the time to access a given block of memory isn't constant (or even nearly so) so it's not really random-access.
(If you want to be really nit-picky, it's random access on reads but not on writes. It can even end up being more complicated since you can have a read queued behind a erase on some flash devices)