Signal pickup.

What is it?
This is where your CB signal is picked up by something which is not intended to be an antenna.
The most common and obvious case of this would be in stereo systems, although it can also be the cause of interference to television and radio equipment.

What can suffer from signal pickup?
Basically, any electrical or electronic equipment.
Equipment which is not designed to receive radio signals (such as stereo systems and computers) can only suffer interference due to this - harmonics and spurious emissions are NOT even a consideration with such equipment.

Tip. Interference to other equipment is the usual reason for a visit from enforcement agencies. Even if you are not to blame for interference, you would get busted for any illegal equipment found.

Who's fault is it?
As the equipment suffering the problem should not be picking up ANY radio signals at that point, it has to be the fault of the equipment getting the interference - the stereo, etc.
However, there are things that can be done with the CB system to minimise the chances of this problem happening.

What causes it?
This is caused by wires, leads, PCB tracks, etc. on the affected equipment acting as an antenna, picking up the radio signal, and feeding it into the internal circuits where the problem may give a noise, distorted sound, or clear reproduction of the CBers voice.

What should I do about it?
The key to curing this problem or, better still, minimising the chance of it happening in the first place, is to reduce the amount of CB signal getting to other electrical and electronic equipment. Measures possible include:

Antenna position:
Wherever possible, your antenna should be mounted as high as possible, above any other electrical equipment and antennas.

Coax.
The use of old or cheap coax may cause more signal to be radiated by the coax, rather than the antenna. This signal may be picked up by other equipment, rather than other CBers. The position of your coax can also be important. It should not be placed near to other electrical or electronic equipment or cables.

Antenna tuning:
Poor tuning of the antenna can cause the coax to radiate signal, which will be lower to the ground and closer to other equipment. It is in your favour to make sure that as much of your signal as possible is sent out at the antenna.

Do not leave your SWR meter in line:
As the SWR meter can cause losses, it should only be connected while testing the antenna.

Filtering:
Filters can be added to the equipment suffering with the interference.