Gobsmacked

Gobsmacked: a truly British expression meaning to be shocked and surprised beyond belief. The expression is believed by some to come literally from ‘gob’ (a British expression for mouth), and the look of shock that comes from someone hitting it.

• I was gobsmacked when she told me she was pregnant with triplets. [Eu estava chocado quando ela me disse que estava grávida de trigêmeos.]

Fonte: Lifehack.