Technically, a retrograde orbit is an orbit with an inclination of more than 90°. More usually, an orbit with an inclination a lot over 90 degrees. Almost no satellites are launched into retrograde orbit because the quantity of fuel required to launch them is much greater than for a prograde orbit. This is because when the rocket starts out on the ground, it already has an eastward component of velocity equal to the rotational velocity of the Earth at its launch latitude. To get to orbital velocity, the difference between the orbital velocity and the rotational velocity on the ground has to be made up. However, if you want to go westwards, you have to make the same change in velocity, plus twice the Earth's rotational velocity at launch.
