1. To make something stronger, sturdier, or more resilient by additional materials or supports. We need to reinforce this wall with steel beams, or else it could come crashing down under the weight of the house. They started reinforcing the barricade with anything heavy they could find in the house.

2. To give a military force greater strength by adding more troops, personnel, equipment, etc. We'll hopefully be able to reinforce our active squadrons with more soldiers by the end of the month. The new spending bill aims to reinforce troops on the ground with more advanced weaponry and communications equipment.

3. To make some feeling or thought process stronger, more effective, or more forceful with the addition of supporting evidence or action. These kinds of people simply reinforce their prejudices with cherry-picked information that omits or ignores anything that goes against their own narrative. It's important to reinforce your child's sense of safety and wellbeing with displays of affection and words of encouragement.