Pronunciation: (in-jek'shun),[key] —n. 1. the act of injecting.
2. something that is injected.
3. a liquid injected into the body, esp. for medicinal purposes, as a hypodermic or an enema.
4. state of being hyperemic or bloodshot.
5. Math.a one-to-one function.
6. Also called insertion.Aerospace.the process of putting a spacecraft into orbit or some other desired trajectory.