Final answer:
D.B.B stands for 'Degree of Bend Back' in conduit bending, which refers to the elongation or stretching of a conduit during the bending process.
Step-by-step explanation:
The abbreviation D.B.B in conduit bending stands for 'Degree of Bend Back.' In conduit bending, when a conduit is bent, it needs to be elongated or stretched to make up for the length of pipe that is lost in the bend. The D.B.B is the measurement of how much the conduit is elongated during the bending process.
For example, if the D.B.B is 5 inches, it means that the conduit needs to be stretched or elongated by 5 inches during the bending process to compensate for the length lost in the bend.