If someone has a stutter, they find it difficult to say the first sound of a word, and so they often hesitate or repeat it two or three times. He spoke with a pronounced stutter. = stammer
If someone stutters, they have difficulty speaking because they find it hard to say the first sound of a word. I was trembling so hard, I thought I would stutter when I spoke. = stammer + stuttering stut·ter·ing He had to stop talking because if he'd kept on, the stuttering would have started
If something stutters along, it progresses slowly and unevenly. The old truck stuttered along the winding road The political debate stutters on. an inability to speak normally because you stutter = stammer