• (КАК <БУДТО, СЛОВНО, ТОЧНО> АРШИН ПРОГЛОТИЛ coll, humor
[(как etc +) VP; adv (variants with как etc) or predic with subj: human (all variants); past only; fixed WO]
=====
⇒ (a person who) has unnaturally straight posture (may refer to a permanent or a temporary characteristic):
- straight as a ramrod;
- ramrod-straight;
- stiff as a poker;
- (one) looks like he has a broomstick <a poker> up his butt.
♦ "Я вот чего хотел-то: разводец бы нам организовать... Да что ты молчишь?" - как будто удивился [Дмитрий]... А она [Маруся] стоит и крикнуть не может... Ведь её - Дмитрий! Как же так?.. "Ну вот, будешь теперь стоять, как аршин проглотила..." (Суслов 1). "What I wanted was this: we should get a divorce. ...Why are you so quiet?" he [Dmitry] asked, as if he were surprised. ...And she [Marusia] stood there and couldn't cry out. ...It was her Dmitry! How could this be?..."So now you just stand there, stiff as a poker" (la).
—————
← "Аршин" is an old Russian measure of length (0.71 meter). The term also refers to a stick or ruler of that length (formerly used by merchants, tailors etc).
Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. С.И. Лубенская. 2004.