The Collaborative International Dictionary of English v.0.48:
Antenna \An*ten"na\, n.; pl. Antenn[ae]. [L. antenna
sail-yard; NL., a feeler, horn of an insect.]
1. (Zool.) A movable, articulated organ of sensation,
attached to the heads of insects and Crustacea. There are
two in the former, and usually four in the latter. They
are used as organs of touch, and in some species of
Crustacea the cavity of the ear is situated near the basal
joint. In insects, they are popularly called horns, and
also feelers. The term in also applied to similar organs
on the heads of other arthropods and of annelids.
2. (Electronics) A metallic device, variously shaped,
designed for the purpose of either transmitting or
receiving radio waves, as for radio or television
broadcasting, or for transmitting communication signals.
Some types are: whip antenna, antenna tower, horn
antenna, dish antenna, directional antenna and
rabbit ears. See transmitter, receiver.