What is incomplete dominance?:
 Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant is not completely dominant over the other allele. This result in a combined phenotype.
Examples:
In cross-pollination experiments between red and white snapdragon plants, the resulting offspring are pink. The dominant allele that produces the red color is not completely expressed over the recessive allele that produces the white color.


Bibliography:
http://biology.about.com/od/geneticsglossary/g/incompletedom.htm