This is referred to as wraparound, since the top and bottom of the screen wrap around to meet, as do the left and right sides (topologically equivalent to a Euclidean 2-torus).
[2] Others such as Pac-Man, Wizard of Wor, and some games in the Bomberman series, have a boundary surrounding most of the playing area, but have a few paths connecting the left side to the right, or the top to the bottom, that characters can travel on.
Wraparound can apply to scrolling games such as Defender, where the player can infinitely fly in one direction because the horizontal extents of the landscape are connected.
Wraparound was common in games throughout the 1970s and early 1980s, including Space Race (1973), Combat (1977), Asteroids (1979), and Star Castle (1980).
Instead of creating expansive environments that required significant memory or processing power, developers utilized wraparound to simulate continuous gameplay on limited hardware.