Definition: shock rating
With regard to computers, it typically refers to the measurement of a hard disk's ability to withstand being dropped on the floor. Measured in Gs (acceleration), the average desktop hard disk rates between 100 and 200 Gs in a non-operating state. It can be dropped up to a foot without damage, depending on the floor surface.
Laptop drives have a higher G rating, and extremely ruggedized drives can measure up to 10,000 Gs, which means the computer can literally be thrown across a room. However, when the drive is in use, it is much more vulnerable, which is why the type of measurement must be equal when comparing models: operating vs. operating, non-operating vs. non-operating.