Groupthink
Etymology
Coined by the journalist William H. Whyte in 1952 as a deliberate echo of the sinister compounds in Orwell’s "1984," and later developed into a rigorous theory by the psychologist Irving Janis. The Orwellian ring was the point: it names conformity dressed up as agreement.
noun · /GROOP-think/
A mode of group decision-making in which the desire for harmony overrides realistic appraisal of alternatives.
What it names
A specific failure of collective reasoning — consensus achieved by suppressing doubt — that explains many disasters no single member wanted.
Example
Groupthink kept anyone from voicing the obvious risk, since raising it would have broken the room’s confident mood.
Related idea
Groupthink is the internal pressure within a cohesive group to converge and silence dissent; the bystander effect is the diffusion of responsibility among people who may not even know each other — both are failures of the group, but one suppresses judgment and the other suppresses action.