Cursed is a status which makes it so that the next equipment used has a 50% chance to fail. This also removes the equipment from play during the turn, so reusable equipment that gets cursed is lost until the next turn.
The effect is reduced by 1 per each equipment that fails, and is fully removed at the end of the cursed user's turn.
In the Parallel Universe episodes, Curse is changed to Curse?. This status is makes it so that the next equipment used has a 50% chance to switch targets. This means, for example, that items that hit the enemy will now hit the user instead, and items that return dice will instead give dice to the enemy.
This effect does not prevent reuseable equipment from being reused, unlike regular Curse.
Some equipment can't be cursed at all, usually to prevent game-breaking glitches happening from the target-swapping that Curse? does.