Tyranny of the majority
Etymology
The phrase was popularized by Alexis de Tocqueville in "Democracy in America" (1835) and by John Stuart Mill in "On Liberty" (1859), both warning that democratic majorities could crush individual freedom as surely as any despot. The worry is older, but these two fixed the phrase in political vocabulary.
noun phrase · /TEER-uh-nee uv thuh muh-JOR-ih-tee/
The oppression of a minority by a majority that uses democratic legitimacy to trample dissenting rights and interests.
What it names
A crucial corrective to the assumption that majority rule is automatically just — it names how counting heads can become a weapon against the outnumbered.
Example
Constitutional rights exist precisely to guard against the tyranny of the majority, so that a fifty-one percent vote cannot strip the other forty-nine of their liberties.
Related idea
The mirror image of majoritarianism, the principle that the majority should simply prevail; this phrase names what goes wrong when that principle runs unchecked by protected rights.