Definition of precipitation for English Language Learners : water that falls to the ground as rain, snow, etc. : the process of separating a solid substance from a liquid
There is no standard unit of volume. In the US, a shot is 1.5 ounces and a small shot is 1 ounce of liquor for an alcoholic beverage such as whiskey. However, this varies internationally and there is no absolutely defined unit, and various sizes of glasses are used.
Use a tablespoon. A single 'shot' can vary from 20 to 60 mL, depending upon which country[1] you live in. I'll assume you are in the US, in which case a single shot is defined as 44 mL or 1.5 fluid ounces. 1 tablespoon equals 14.7868 mL. Use three of them, and that is ~44 mL.