adverb, adverb taking the 'to' particle
stumbling over words; fumbling one's speech; stuttering
Describes the manner of speaking haltingly, often due to nervousness or lack of fluency. Frequently used with 言う or 話す.
緊張して、かみかみでスピーチをしてしまった。
I was so nervous that I ended up giving the speech while stumbling over my words.
彼はいつもかみかみと話す。
He always speaks with a stutter.
どもる is a verb meaning 'to stutter' as a speech disorder or habit, while かみかみ is an adverb describing the manner of fumbling words, often due to temporary nervousness.
Reduplication of 噛む (かむ, 'to bite'), literally 'biting biting', suggesting the image of one's words getting caught as if biting them. The exact derivation is uncertain, but it is a colloquial mimetic expression.