vertical direction
direction that is perpendicular to the horizontal plane; direction connecting "up" and "down"
en-GB/ˈvɜːtɪkl dɪˈɹɛkʃn/
en-US/ˈvɝdɪkəl dɚˈɛkʃən/
direction that is perpendicular to the horizontal plane; direction connecting "up" and "down"