1. n. 
A representation of the integrity of the cement job, especially whether the cement is adhering solidly to the outside of the casing. The log is typically obtained from one of a variety of sonic-type tools. The newer versions, called cement evaluation logs, along with their processing software, can give detailed, 360° representations of the integrity of the cement job, whereas older versions may display a single line representing the integrated integrity around the casing.
Alternate Form: cement evaluation log
2. n. 
A log that uses the variations in amplitude of an acoustic signal traveling down the casing wall between a transmitter and receiver to determine the quality of cement bond on the exterior casing wall. The fundamental principle is that the acoustic signal will be more attenuated in the presence of cement than if the casing were uncemented. The measurement is largely qualitative, as there is no indication of azimuthal cement variations such as channeling, and as it is sensitive to the effect of a microannulus.
See: pulse echo