v. To verbally assault, especially to argue against an opinion, motive, or action; to question the truth or validity of.
the GNU version of the Collaborative International Dictionary of English
v. To attack by words or arguments; to contradict; to assail; to call in question; to make insinuations against; to gainsay; to oppose.
The Century Dictionary and Cyclopedia
To attack by words or arguments; contradict; assail; call in question; gainsay.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
v. attack as false or wrong
Word Usage
""impugn" Mr Needham under parliamentary privilege, the CMC was proving its independence by holding a public inquiry into a former ministerial staffer."