Definition from Wiktionary, the free dictionary
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stonewall (plural stonewalls)
- A refusal to cooperate.
- (informal) To refuse to answer or cooperate, especially in supplying information.
- At the press conference, the Prime Minister appeared to be stonewalling when asked about tax increases.
Derived terms 
stonewall (not comparable)
- (UK, idiomatic) Certain, stone cold.
Usage notes 
- Most often encountered in sports, in reference to refereeing decisions; apparently a corruption of "stone cold".