1. Absolutely necessary or crucial. "It is imperative that the report is finished by Friday, so we can send it to the client." 2. An order or command. "The workers were left with the imperative from their boss to work hard and try your best." Read more
Kant's moral theory comes down to what is called "the moral imperative," which states that one ought not perform an action unless one feels it is permissible for everyone to perform that same action.