Other forms: reintegrated; reintegrating; reintegrates
When something that was once unified comes back together again, it reintegrates. When you move to Mexico, you'll need to reintegrate that Spanish you learned as a child back into your vocabulary!
To integrate something is to combine it with something else to form a whole, the way a preschool tries to integrate fun and learning into every single day. When an element has broken away from that whole, you can reintegrate it by restoring it. Your school district, for example, might reintegrate music into the curriculum after budget cuts removed it for several years.