means A device that generates and sends out signals — radio waves, electrical pulses, or data — so they can travel to a distant receiver.

from From Latin 'transmittere,' to send across: 'trans-' (across) plus 'mittere' (to send), the same restless verb behind 'missile,' 'mission,' and 'emit.' The '-er' simply names the thing that does the sending. The word existed long before radio, but it found its calling in the early days of wireless telegraphy, when machines first learned to fling messages across empty air.