Having frequent or customary intercourse; intimately associating; familiar by companionship; acquainted: followed by with, formerly also by among.Acquainted by familiar use or study; having a thorough or intimate knowledge or proficiency: followed generally by with, formerly and still occasionally by in.Having concern or connection; concerned, occupied, or engaged: followed by with or about.Synonyms Versed (in), skilled (in), proficient (in).