"Abnormal proliferation" refers to an excessive and uncontrolled growth or increase in number of cells or organisms, which is not normal or healthy.
Full definition
Lymphomas are caused by
an abnormal proliferation of white blood cells and can occur at any age.
Because, of course, it is
this abnormal proliferation of blood vessel cells, which we term angiogenesis, in the back of the eye that is the key feature of wet AMD.
Cancer begins through mutations at the cellular level, which leads to
an abnormal proliferation of abnormal cells.