To the fingertips is an idiom that describes someone who is expertly skilled or knowledgeable in a particular area. Some synonyms for this phrase are "thoroughly acquainted," "fully versed," "adept," "proficient," "skilled," "competent," and "expert." These words emphasize someone's deep understanding and proficiency in a particular field. Additionally, terms like "masterful," "informed," "well-versed," and "well-informed" also capture the essence of this phrase. Whether you're describing a musician, athlete, or scholar, using these synonyms can add depth and precision to your language and more accurately convey the depth of someone's knowledge or skill.