Incomplete dominance is the result of a dominant gene not fully dominating the recessive gene. For example, in some species of flowers, crossing a red flower with a white flower results in a pink flower. This happens because the gene that tells a flower to be red doesn't completely overshadow the gene that tells the flower to be white, creating a flower that is pink. You can find more information here: http://www.newton.dep.anl.gov/askasci/mole00/mole00373.htm
