семи пяденей во лбу

• СЕМИ <СЕМЬ rare> ПЯДЕЙ <ПЯДЕЙ obsoles, ПЯДЕНЬ obs, ПЯДЕНЕЙ obs> ВО ЛБУ coll

[NPgen or NP, these forms only; usu. subj-compl with быть, subj: human (var. with семи; var. with семь is used as subj with быть or obj of иметь; usu. condit будь кто семи пядей во лбу; fixed WO]

=====

⇒ one is very intelligent, quick-witted, has remarkable abilities:

- будь X семи пядей во лбу{{}}≈ be X <even if X were> a genius <a real brain, the smartest man in the world>;

- be X <even if X were> (as) wise as an owl <(as) shrewd as a fox, (as) wise as Solomon, (as) smart as a whip>.

     ♦ [Чугунов:] Будь ты хоть семи пядей во лбу, да коли законов не знаешь... [Павлин:] Понимаю я-с (Островский 5). [Ch.:] You can be as wise as an owl, but if you don't know the law... [R:] I understand, sir (5b).

     ♦ "Кто из моих людей смеет обижать сироту? - закричал он. - Будь он семи пядень во лбу, а от суда моего на уйдёт" (Пушкин 2). "Who among my men dares mistreat an orphan?" he cried. "Be he as shrewd as a fox, he won't escape my judgment'" (2a).

—————

← "Пядь" is an old unit of length equal to the distance between the tips of the thumb and the index finger when they are extended.