From AMS Glossary
(Or, simply, dipole.) A type of antenna for transmitting or receiving electromagnetic radiation, most often in the radio frequency band.
The term dipole antenna has no necessary connection with dipole radiation in the sense usually meant in electromagnetic theory but arises from configuration: A dipole antenna is essentially two thin (diameter much less than length) conductors or poles separated by a gap by means of which an oscillating electric current is fed into (or out of) them. If the total length of the two poles is much less than the wavelength of their radiation, the dipole antenna is sometimes called a short dipole, the source of the term dipole radiation (radiation from an ideal oscillating dipole of negligible extent). Sometimes dipole antenna means an antenna with a length of half the wavelength, but a more precise term is half-wave dipole. The defining characteristic of a dipole antenna is its two identical components, not its length.