Tanāfur al-Kalimāt (تنافر الكلمات) is awkwardness caused by putting individually acceptable words together. Repeated or tightly clustered sounds make the utterance cumbersome.
The source offers a line containing وليس قربَ قبرِ حربٍ قبرُ
And there is no grave beside Ḥarb's grave.
The close recurrence of qurb, qabr, and Ḥarb makes delivery difficult. This differs from Tanāfur al-Ḥurūf: the former is a defect across words; the latter is inside a single word.