Other forms: interdicted; interdicts; interdicting
Interdict means to forbid, to nix, to veto. If your parents find out you're planning a party for a time when they're away , they will interdict it.
If your principal has interdicted gum-chewing at school, he might set up a few random check points, interdicting gum-chewing students with detentions and a command to instantly spit out their offensive, long-lasting candy. To interdict, pope-style, is to in essence excommunicate, or prohibit a person or especially a place from the functions and privileges of the church.