stone wall

(noun) a fence built of rough stones; used to separate fields.

(verb) obstruct or hinder any discussion. Synonyms: stonewall. Examples: "Nixon stonewalled the watergate investigation." "When she doesn't like to face a problem, she simply stonewalls."

(verb) engage in delaying tactics or refuse to cooperate. Synonyms: stonewall. Example: "The president stonewalled when he realized the plot was being uncovered by a journalist."