gobsmacked

今日の単語は"gobsmacked"という見慣れない単語なんですが、先に言ってしまうと、

びっくり仰天した、驚いた

（ランダムハウス英和辞書）

という意味で、イギリス英語の俗語だそうです。

用例として、やはりイギリスの大衆紙The Sunからですが、以下の記事をどうぞ。

SCHOOLS in England have been told to allow kids back to class even if they refuse to be tested for Covid.

（中略）

However, some schools have been accused of "blackmailing" parents by telling them students must be tested in order to return from March 8.

Val Mason, head teacher at Hornchurch High School in Havering, east London, wrote to parents saying children whose parents do not consent to testing will have to work remotely from a "separate space" on the school site.

（中略）

One parent told The Telegraph he was "gobsmacked", adding: "This is coercion bordering on blackmail.

(Alice Fuller. Schools in England told to allow kids back to class even if they refuse Covid test. The Sun, March 4, 2021.)

"gobsmacked"のgob-とは口（くち）のことで、"smack"は叩く、ピシッと打つという意味の動詞です。

口を叩かれるというのはよくわかりませんが、口の周り、頬の辺りを叩かれて唖然としているイメージでしょうか。