phenylthiocarbamide

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A crystalline compound, C₆H₅NHCSNH₂, that tastes intensely bitter to people with a specific dominant gene and is used to test for the presence of the gene.

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

• noun organic chemistry The N-phenyl derivative of carbamide; it is either tasteless or has a bitter taste, depending on the genetic makeup of the person tasting it