Undermine/ˌʌndərˈmaɪn/ Definition 1 of 2Pro Tip 1/3Subtle Weakening Undermine suggests a gradual process, not an immediate effect. His jokes about her work began to slowly undermine her motivation. Pro Tip 2/3Hidden Motives Actions that undermine often appear harmless at first. Smiling, he shared the team's plans with the rival, aiming to undermine their success. Pro Tip 3/3Connotation of Betrayal Undermine can imply betrayal, as trust is broken. By spreading rumors, she began to undermine his reputation among his friends.