A false friend is someone who pretends to be a friend but is actually untrustworthy. A BACKSTABBER is an 11-letter term for someone who betrays a friend by speaking ill of them behind their back. JUDAS is a 5-letter term for someone who betrayed Jesus in the Bible. RAT is a 3-letter term for someone who informs on another person. USER is a 4-letter term for someone who takes advantage of another person. TRAITOR is a 7-letter term for someone who betrays their country, cause, or political party. Iago is a 4-letter term for a character in Shakespeare's play Othello who betrays his friend. Twotimer is an 8-letter term for someone who is unfaithful in a relationship. Snakeinthegrass is a 15-letter term for someone who is sly and deceitful.