conspiracy of silence

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An agreement, either formal or tacit, between two or more parties not to discuss some matter nor to reveal any information concerning it, especially in order to avoid blame, embarrassment, or other discomfort.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a conspiracy not to talk about some situation or event