Militaristic means emphasizing readiness to wage war. A militaristic government is focused on building up its armed forces, and often acts aggressively toward other countries.
When members of an army are regularly seen marching through city streets, you can describe that city as militaristic. And a government's militaristic administration will use strong rhetoric to threaten other countries and place a high importance on funding and preparing arms and soldiers in case of war. Through history, militaristic states have typically been interested in expanding in size or power.