In John 6:70-71, we read "Jesus answered them, 'Did I not choose you, the Twelve? And yet one of you is a devil.' He spoke of Judas the son of Simon Iscariot, for he, one of the Twelve, was going to betray him." My question is, When Jesus says Judas "is a devil," is he saying he was an actual devil, like a "demon"?
No, he is speaking figuratively. He means, in essence, that one of you is being influenced by the devil, or acting like a devil. Similarly, if someone calls a child a "little devil," he probably refers to the headstrongness or naughtiness of the child. (Not his connection with Satan!)