"Precipitation rate" refers to the speed or amount at which rain, snow, or other forms of moisture fall from the sky. It is a measurement of how quickly water is being deposited onto the Earth's surface from the atmosphere. Full definition
They found that upon ending the experiment, the planet would experience a rapid increase in global mean temperature, along with increases in global mean precipitation rate and decreases in sea ice cover. (scientificamerican.com)
The globally averaged intensity of extreme precipitation also changes more rapidly than the globally averaged precipitation rate. (pacificclimate.org)
Understanding how the global - mean precipitation rate will change in response to a climate forcing is a useful thing to know. (hannahlab.org)