The end of a polypeptide chain with the unattached carboxyl group (a -COOH group). Each amino acid in the middle of the chain has an amino group (a -NH2 group) on one side (which is attached to the carboxyl group of the previous amino acid) and a carboxyl group on the other side (which is attached to the amino group of the next amino acid). The other end of the polypeptide chain is called the amino terminal.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.