Horizontally

Unlike waves that break along the shore, Rossby waves are huge, undulating movements of the ocean that stretch horizontally across the planet for hundreds of kilometers in a westward direction.

Source: tatoeba (6682958)

If the moon landing was real, they ask, why didn't the lander scatter dust when it touched down? In reality, the lander was traveling horizontally much of the time and the thrusters that controlled its landing were not pointed down. Radiation from the sun also made the dust highly charged and it clung to the moon’s surface.

Source: tatoeba (8125280)

In the window opening he set small branches about an inch in diameter both vertically and horizontally, and so woven that they formed a substantial grating that could withstand the strength of a powerful animal.

Source: tatoeba (8823082)

The knight moves in the shape of the letter "L": two squares vertically and one horizontally, or one square vertically and two horizontally.

Source: tatoeba (9949465)