ex ‧ pan ‧ sion ‧ is ‧ m AC /ɪkˈspænʃ ə nɪz ə m/ BrE AmE noun [uncountable]
when a country or group increases the amount of land or power that they have – used especially to show disapproval:
military expansionism
—expansionist adjective
—expansionist noun [countable]