A type of polymer (large molecule which consists of a chain of similar smaller molecules called monomers) where all of the monomers are the same thing. For example, a polypeptide which consists entirely of the amino acid lysine linked end to end, instead of many different amino acids linked end to end, would be a homopolymer.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.