up to —— Thoroughly acquainted with; expert or versed in; possessing a thorough knowledge of.
expert or versed, well informed or instructed, in a subject, matter, work, etc. colloquial.
= up in —— at sense 18 above). colloquial (originally U.S.).
英语词典包含1132095条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。