takes する, intransitive verb, noun, adjectival noun or quasi-adjective

  1. to be stumped, to be at a loss, to be at one's wits' end, to be nonplussed.
  2. to be fed up, to be tired (of), to be unable to bear, to be annoyed.

Variations

Pronunciation Kanji Kana Is Common
閉口 へいこう

Contained Kanji Breakdown

closed, shut
と.じる ヘイ し.める (6th, N3)
gate, counter for cannons
モン かど と (2nd, N2)
genius, years old, cubic shaku
サイ (2nd, N3)
hand, hand radical (no. 64)
シュ
mouth
くち コウ ク (1st, N4)