[Antennas] Unity Gain?

[Dan Richardson]

 From time to time an antenna manufactures will state that an antenna has 
"unity gain". It is my understanding that this term is used for describing 
antennas used in mobile applications and is referenced to the gain of a 
quarter-wave whip.
Does anyone know of any instances where this term is used otherwise?

My reason for asking is that I have a so called unity gain antenna, but 
when comparing it to a standard quarter-wave whip it has much less gain.

Danny, K6MHE