The cell line from which egg or sperm cells (gametes) are derived
Definition from: GeneReviews
from the University of Washington and the National Center for Biotechnology Information
A germ line is the sex cells (eggs and sperm) that are used by sexually reproducing organisms to pass on genes from generation to generation. Egg and sperm cells are called germ cells, in contrast to the other cells of the body that are called somatic cells.