שַׂר־חֲמִשִּׁ֖ים וּנְשׂ֣וּא פָנִ֑ים וְיוֹעֵ֛ץ וַחֲכַ֥ם חֲרָשִׁ֖ים וּנְב֥וֹן לָֽחַשׁ׃
Rashi on Isaiah
counsellor One who knows how to intercolate the years and fix the months.
Rashi on Isaiah
skillful craftsman [explained by the Talmud as “wise of the deaf,” meaning that] when he commences [to speak of] words of Torah, all become as deaf [i.e., unable to refute his statement].