There are several synonyms for the phrase "leave out of account," including disregard, overlook, discount and ignore. These synonyms generally indicate a sense of neglect or dismissal of something important, such as an idea, concept or factor. Disregard implies a conscious decision to not pay attention to something, while overlook indicates a failure to notice something that may have importance. Discount implies that something is considered less important that something else, while ignore indicates a deliberate decision to not acknowledge something. In any case, these synonyms all indicate a lack of attention or consideration towards something, and can sometimes lead to errors or oversights.