1. Repetition or doing something again: "reheat," "reprint."
2. Backward movement or direction: "retreat," "reverse."
3. Opposition or against: "rebel," "revolt."
4. Intensity or emphasis: "remarkable," "renowned."
5. Renewal or restoration: "regenerate," "rebirth."
6. Reversal or undoing: "rectify," "reconsider."
7. Repetition in music: "refrain."
8. Back or beyond: "remote."
9. Again or anew: "revive."
10. Together or with: "reunite," "relate."
The specific meaning of "re-" in a particular word depends on the context and root it's attached to.