In Bicycle terms:
The hybrid bicycle first appeared on the market in 1990. It is a cross between a road bicycle and a mountain bicycle. The hybrid bicycle has a frame geometry that is responsive like that of a road bike, but with the ruggedness, maneuverability and comfort of a mountain bike. At that time, it was indeed lighter than the mountain bicycle at 27 lbs. One of the first companies that produced this type of bicycle was Miyata with their Alumicross and Triplecross models. The Alumicross was made of bonded aluminum and the Triplecross was made of high-tensile steel with lugs. other companies such as Cannondale and Mongoose followed the trend. Now known as the city bicycle, its presence has not died. Here are its general specifications to differentiate it from other types of bicycles:

Hybrid Specs.:
Frame - steel or aluminum
Components - Shimano/SRAM mountain grouppos
brakes - cantilever, "V" brake or disc brakes
pedals - usually flat pedals to accomodate normal sneakers
drivetrain - 21 + speed (w/ 3-ring chainrings)
Handlebars - flat, mountain bike style
Saddle - usually mountain style with extra padding
Wheels and tyres - 700C x 30 to 35