majority rule

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A doctrine by which a numerical majority of an organized group holds the power to make decisions binding on all in the group.

Wiktionary

1. n. A decision rule whereby the decisions of the numerical majority of a group will bind on the whole group.

GNU Webster's 1913

1. n. The rule or doctrine that the numerical majority{2} of an organized group can make decisions binding on the whole group. Contrasted with unanimous consent, or decision by a decree of a single person or small committee forming part of an organization.

WordNet 3.0

1. n. the doctrine that the numerical majority of an organized group can make decisions binding on the whole group