dispute the truth, validity, or honesty of (a statement or motive); call into question
(对真实、有效或诚实等)质疑,怀疑
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the father does not impugn her capacity as a good mother .父亲不怀疑她作为一位好母亲的能力。
 
"late Middle English (also in the sense   ‘assault, attack physically’):  from Latin 
