It generally implies action or process of throwing or casting something.
Here are some common examples:
* Inject: To throw something into (e.g., inject medicine)
* Eject: To throw something out (e.g., eject a CD from a player)
* Project: To throw something forward (e.g., project a movie onto a screen)
* Subject: To place under something, or to throw something under (e.g., subject someone to an experiment)
The suffix "-ject" is often used in scientific and technical contexts, but it can also appear in more general terms.