Short for constant linear velocity, a method used by most older CD-ROM players to access data. With CLV, the rotation speed of the disk changes based on how close to the center of the disk the data is. For tracks near the center, the disk rotates faster, and for data on the outside, the disk rotates slower.
The purpose of CLV is to ensure a constant data rate regardless of where on the disk the data is being accessed. Because less data can fit on the inside tracks, the disk needs to rotate faster for these areas
An alternative technology, which is becoming increasingly popular, is CAV (Constant Angular Velocity).
Also see zoned CLV.