verbigerate

from The Century Dictionary.

• In pathology, to utter repeatedly certain words or phrases, without regard to their sense.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb obsolete To talk; chat.
• intransitive verb (Med.) To repeat a word or sentence, in speaking or writing, without wishing to do so or in spite of efforts to cease.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb intransitive To repeat meaningless words and phrases, especially as a symptom of mental illness.