For amplifiers, slew rate is typically defined as the rate of change of the output of the amplifier, and is measured in voltage over time. The slew rate value in the device-specific data sheet is an overall maximum measured in the specified configuration. Usually this configuration is a large input step with a low gain. Data sheets often do not provide further information for other configurations.

Slew boost is additional circuitry that allows for much higher slew rates than otherwise possible in standard amplifier architecture. It is very common for a high speed amplifier to have some sort of slew boosting circuit. However, specific slew boost architecture is not published in data sheets - in fact, it is often not disclosed if the part has slew boost or not. This adds another layer of uncertainty to the slew rate value of your specific application as slew boosting architectures may perform differently depending on how they were implemented.