The Only Use of

recede
in
The Veldt

Now, as George and Lydia Hadley stood in the center of the room, the walls began to purr and recede into crystalline distance, it seemed, and presently an African veldt appeared, in three dimensions, on all sides, in color reproduced to the final pebble and bit of straw.
p. 4.6

recede = move away

Definition:

to move away or diminish (become less)

The exact meaning of recede depends upon its context. For example:

"We can't move back in until the floodwaters recede." -- diminish and move away
"Her fear receded." -- diminished
"The waves first advance and then recede." -- move away
"The news story receded into the background as it was replaced by new stories." -- received diminished attention
"a receding hairline" -- diminished hair (each year the line where hair stops growing is higher on the forehead)
"She has a receding chin." -- sloping back (as contrasted to sticking out)