He 'stuttered' [='stammered'] something that I didn't understand.
He has a 'stutter'. = He speaks with a 'stutter'. [=he stutters]
He had speech therapy for his 'stuttering'.
(..) You faked his death! We had a funeral. We buried him. And now you're asking for my help? Go to hell. Okay, now what do you know? I'm sorry. Did I stutter? I told you. Everything. What do you know? I know you do experiments on kidnapped little kids, whose parents' brains you've turned to mush. (..)2016 TvShow: Stranger Things Title: Chapter Eight: The Upside Down Season: 1 Episode 8