1. See upright. 1. horizontal. 1  being in a position or direction perpendicular to the plane of the horizon; upright; plumb. 2  of, pertaining to, or situated at the vertex. 3  Anatomyof or pertaining to the cranial vertex.
Last Updated: Radio wave, wave from the portion of the electromagnetic spectrum at lower frequencies than microwaves. The wavelengths of radio waves range from thousands of metres to 30 cm. These correspond to frequencies as low as 3 Hz and as high as 1 gigahertz (109 Hz).
It's simple. Radio waves travel unbelievably fastâat the speed of light (300,000 km or 186,000 miles per second). Analog radio. Ocean waves carry energy by making the water move up and down. In much the same way, radio waves carry energy as an invisible, up-and-down movement of electricity and magnetism.