A measurement in cm3 refers to the number of cubic centimeters. Cubic centimeters are a measurement of volume, and a cubic centimeter is equivalent to a milliliter.
A cubic centimeter, or milliliter, is a unit of volume equivalent to the space that a box would take up if it were one centimeter in length, width and height. A cubic centimeter is 1/1000000 the volume of a cubic meter, or 1 * 10^-6 the volume of a cubic meter. It is also 1/1000 the volume of a liter. Cubic centimeters are sometimes referred to as "cc's," a common term used in medicine when describing units of volume such as blood or a drug.