to put a liquid or gas back somewhere, especially liquid into a person's body using a needle and syringe (= small tube)

The tissue is mixed with white blood cells before being reinjected into the patient's body.

After they remove the blood, they filter it before reinjecting it. 抽血后，他们会对其进行过滤，然后再重新输入。

The contractors were ordered to re-inject the water into the ground.

to put something that had been lost or removed back into a situation or process

The new owners have promised to reinject some life into the business.

The author is trying to re-inject idealism into the political process. 作者试图将理想主义重新注入政治进程。