In communications, wideband is defined as a higher rate of transmission in contrast to a lower "narrowband" rate. The metrics are different depending on the type of communications, and the lower and upper limits change as time and technology advance forward.
For example, a radio channel of 25 kHz or higher has been considered wideband, and everything below to be narrowband. In digital transmission, rates above T1 speeds (1.544 Mbps) were wideband at one time.
Wide Means Narrow and Short
Wideband implies higher frequency, which is why Verizon calls its high-frequency 5G service "Ultra Wideband." However, high frequencies mean a narrow wavelength and short transmission distance. Narrow and short seem contradictory to the expansive sound of "wide" in wideband, but all of this terminology has been around a long time. Contrast with
narrowband and
broadband. See
wavelength,
5G UWB and
wideband audio.