1. Godan verb with 'mu' ending, Transitive verb

   1.

   to hold between (e.g. one's fingers, chopsticks); to grip (from both sides)

2. 2.

   to put between; to sandwich between; to insert; to interpose

3. 3.

   to catch (e.g. a finger in a door); to trap; to pinch

Example sentences

• 彼は会話の最中に口を挟むことがよくある。

  He often breaks into the middle of a conversation.

• 私が口を挟むことではないのは分かってます。

  I know it's none of my business.