volumenometer

from The Century Dictionary.

• noun An instrument for measuring the volume of a solid body by the quantity of a liquid or of air which it displaces, and thence also for determining its specific gravity.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics) An instrument for measuring the volume of a body, especially a solid, by means of the difference in tension caused by its presence and absence in a confined portion of air.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An instrument which measure the volume (3-dimensional space) of something which can't be immersed in liquid.