守口如瓶

shǒukǒurúpíng
  1. lit. to guard one's mouth like a closed bottle (idiom); tight-lipped
  2. reticent
  3. not breathing a word

CEDICT

to keep one's mouth shut; to remain tight-lipped

Wiktionary

嘴像瓶口一樣封得嚴緊。比喻嚴守祕密。《隋唐演義．第三五回》：「今願陛下守口如瓶，不可提起。」也作「緘口如瓶」。

重編國語辭典

嘴像瓶口一樣封得嚴緊，比喻嚴守祕密

維基詞典

Entry Composition

1 守口 Shǒukǒu
  1. (～市) Moriguchi (a city in Ōsaka prefecture, Japan)
  2. Moriguchi (a city in Ōsaka prefecture, Japan)
2 如 rú
  1. as
  2. as if
  3. such as
=3 瓶 píng
  1. bottle
  2. vase
  3. pitcher
  4. classifier for wine and liquids

classifier: 個
=3 瓶 píng variant of 瓶 píng

Related entries

寡言 guǎyán
  1. taciturn
  2. reticent
沉默寡言 chénmòguǎyán
  1. habitually silent (idiom)
  2. reticent
  3. uncommunicative
林肯本人是沉默寡言的。

Lincoln himself was silent.

Source: Tatoeba

拘束 jūshù
  1. to restrict
  2. to restrain
  3. constrained
  4. awkward
  5. ill at ease
  6. uncomfortable
  7. reticent