هُمَزَةٍ لُمَزَةٍ
One who disparages and finds fault. (الهمزة: 1)
Humazah and lumazah are closely associated descriptions of disparaging conduct. Exegetical explanations distinguish their manner of fault-finding in different ways. Rhetorically their proximity in meaning and patterned sound underscore a persistent habit of belittling others.
It would be unsound to insist that the words are exact synonyms in every respect or to make one debated division between face-to-face and absent-person speech into a fixed grammatical definition. The core condemnation concerns harmful disparagement.