Gotten down cold refers to having something memorized or mastered to a high degree. When looking for antonyms for this phrase, we can consider words that describe the opposite of mastery, such as unfamiliar, unpracticed, or inexperienced. Other antonyms may include terms that suggest a lack of confidence, such as uncertain, unsure, or hesitant. Additionally, the opposite of mastery could be described as forgetting, neglecting, or overlooking something. Therefore, a few possible antonyms for gotten down cold may include novice, forgetful, or unprepared. These words suggest a lack of skill or knowledge, and indicate the opposite of the confidence and expertise associated with mastery.