[shakespeare47]

It's a speech disorder.

Cluttering (also called tachyphemia or tachyphrasia) is a speech and communication disorder characterized by a rapid rate of speech, erratic rhythm, and poor syntax or grammar, making speech difficult to understand.

I'm self-diagnosed, and feel some anxiety related to my speech. I usually do okay, but I do have episodes of poor syntax and grammar (okay, I have issues with virtually everything listed above) as well as slurring my speech at times, especially when I'm tired and/or under stress.

More info:

These fluency and rate deviations are the essential symptoms of cluttering. In addition, however, there are a number of symptoms that may or may not be present but add support to a diagnosis of cluttering. Accordingly, the clinical picture of a typical cluttering problem would be enhanced if the person in question had or manifested any of the following optional characteristics: confusing, disorganized language or conversational skills, often with word-finding difficulties; limited awareness of his or her fluency and rate problems; temporary improvement when asked to "slow down" or "pay attention" to speech (or when being tape recorded); mispronunciations, slurring of speech sounds, or deleting nonstressed syllables in longer words (e.g., "ferchly" for "fortunately"); speech that is difficult to understand; several blood relatives who stutter or clutter; social or vocational problems resulting from cluttering symptoms; learning disabilities not related to reduced intelligence; sloppy handwriting; distractibility, hyperactivity, or a limited attention span; difficulty with organizational skills for daily activities; and/or auditory perceptual difficulties.

And another helpful website.