To take someone for granted means to underestimate or undervalue their importance, efforts, or contributions. Some synonyms for this phrase include to overlook, ignore, neglect, disregard, or dismiss someone's worth or presence. In other words, when we take someone for granted, we fail to appreciate them and often assume that they will always be available or helpful without any effort on our part. It is important to be mindful of our actions and words towards those around us and to express our gratitude and appreciation to those we may have taken for granted in the past.