horizontally
US /ˌhɔːr.ɪˈzɑːn.t̬əl.i/
UK /ˌhɔːr.ɪˈzɑːn.t̬əl.i/

1.
horizontalement
in a horizontal direction or position; flat or level with the ground
:
•
The artist painted the landscape horizontally.
L'artiste a peint le paysage horizontalement.
•
Lay the planks horizontally across the gap.
Posez les planches horizontalement sur l'espace.