o ‧ ver ‧ pop ‧ u ‧ la ‧ tion /ˌəʊvəpɒpjəˈleɪʃ ə n, ˌəʊvəpɒpjʊˈleɪʃ ə n $ ˌoʊvərpɑːp-/ BrE AmE noun [uncountable]
when there are too many people living in a particular place:
efforts to reduce overpopulation
—overpopulated /ˌəʊvəˈpɒpəleɪtəd, ˌəʊvəˈpɒpʊleɪtəd $ ˌoʊvərˈpɑːp-/ adjective :
our overpopulated cities