Disloyal can mean non sincere, dishonest, legal, fraudulent. Usually someone who tells lies, in order to achieve usually something illegal and immoral, in a fraudulent way, thus have a fraudulent intention deriving from evil motives and conscience; also, one who tries by many means to hide his/her illegal, fraudulent acts, usually by saying things he/she does not believe, or make others guilty, while they aren't in order to hide true guilty ones, complices of him/her etc.