What it means

1. verb enlarge, develop, or increase by degrees or in stages
   “build up your savings”
2. verb change the use of and make available or usable
   “develop land”
3. verb form or accumulate steadily
   “Resistance to the manager's plan built up quickly”
4. verb bolster or strengthen
   “We worked up courage”
5. verb prepare oneself for a military confrontation
   “The U.S. is girding for a conflict in the Middle East”