1) Act in opposition to 
• (v. t.) To work in opposition to; to counteract.
A mark, also known as a counterstamp, struck onto an existing coin or the cut part of a coin some time after it was initially struck. An ancient practice, still in use today, carried out usually as an emergency measure to revalue the currency or to validate a foreign piece for use in another country. countermark of George III on a 1785 Spanish-Ame....
Coun`ter·work' (-wûrk') transitive verb To work in opposition to; to counteract. « That counterworks each folly and caprice. Pope. » 
work or action to oppose some other work or action.