omnidirectional

From omni- +‎ directional.

• IPA^(key): /ɒmˈnɪdɪˈɹɛk.ʃə.nəl/, /ɒmˈnɪdaɪˈɹɛk.ʃə.nəl/
• Hyphenation: om‧ni‧dir‧ec‧tion‧al

omnidirectional (not comparable)

1. In every direction, especially of a radio system capable of transmitting or receiving signals in all directions, or of a microphone capable of detecting sound from all directions.

   An omnidirectional radio beacon.

2. (physics, electrical engineering) Having a ring-shaped radiation pattern, with equal radiation in all azimuthal directions.
   • 2004, Harold Davis, Absolute Beginner's Guide to Wi-Fi Wireless Networking, Que Publishing, →ISBN, page 227:

     The radiation pattern of an omnidirectional antenna looks like a doughnut, with the antenna in the center of the doughnut, as depicted in Figure 17.1.

3. (rare) Of such an attack or effect that encompasses all directions.
   • 1959, Air University Quarterly Review, Volumes 11-12‎, U.S. Army Air Forces, page 44:

     The ascendancy of the offensive over the defensive stems particularly from the ability of advanced weapon systems to penetrate enemy defenses. The combination of great speed and great altitude, taken together with numbers during a mass launch, ensures that selected targets will be reached. Improvements clearly possible through the use of decoys, multiple warheads, electronic countermeasures, varying trajectories, maneuverability, feinting, and omnidirectional attack will further increase the ability penetrate defenses.

   • 1962, Missiles and Rockets‎, American Aviation Publications, page 40:

     Any defense posture that he may have that would be common for any ballistic missile would not suffice for a low-altitude omnidirectional high-speed nuclear ramjet missile.

   • 2003, David Weber, Empire from the Ashes‎, Baen Books, →ISBN, page 577:

     He’d known better at the time, damn it, but he’d let himself worry more over the possibility of losing an hour or two than her safety. He pounded his fists together and stared up at the sky with bitter eyes, but the alien stars mocked him, and his jaw clenched as he powered his com implant and sent out a full-powered omnidirectional pulse, heedless of the quarantine system’s sensors.

Because true omnidirectionality is impossible for individual antennas, omnidirectional is generally used in electrical engineering contexts to refer to antennas that can receive signals in all directions in the azimuthal plane. In these contexts, a hypothetical antenna that radiates in all directions equally is called isotropic.

• unidirectional

• isotropic