n. 1 the act or an instance of expanding; the state of being expanded. 2 enlargement of the scale or scope of (esp. commercial) operations. 3 increase in the amount of a State's territory or area of control. 4 an increase in the volume of fuel etc. on combustion in the cylinder of an engine. expansionary adj. expansionism n. expansionist n. expansionistic adj. (all in senses 2, 3).
[ LL expansio (as EXPAND) ]