«ومخالفة القياس: كون الكلمة غير جارية على القانون الصرفي»
Violation of qiyās means that a word does not conform to the relevant morphological rule.
Qiyās ṣarfī covers regular word formation, including plurals, assimilation, and other morphological patterns. A form that departs from the required rule may be treated as a defect under this condition.
This is not the same as sound discord. An irregularly formed expression can be quite easy to pronounce but still fail the morphological criterion.