Polygenic

adj. caused by many genes, resulting from several genes (Genetics)

Inheritance of quantitative traits refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to the interactions between two or more genes and their environment (also called Polygenic inheritance). Though not necessarily genes themselves, quantitative trait loci (QTLs) are stretches of DNA that are closely linked to the genes that underlie the trait in question. QTLs can be molecularly identified (for example, with PCR) to help map regions of the genome that contain genes involved in specifying a quantitative trait. This can be an early step in identifying and sequencing these genes.
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Adjective
1. of or relating to an inheritable character that is controlled by several genes at once; of or related to or determined by polygenes
(similar) inheritable, heritable
(classification) genetics, genetic science

(a.)
Of or relating to polygeny; polygenetic.
  

Traits controlled by two or more genetic loci. They are usually influenced by environment as well (multifactorial).