From Merriam-Webster's:
http://www.britannica.com/cgi-bin/dictionary?va=majority
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Main Entry: ma�jor�i�ty
Pronunciation: m&-'jor-&-tE, -'j�r-
Function: noun
Inflected Form(s): plural -ties
Date: 1552
1 obsolete : the quality or state of being greater
2 a : the age at which full civil rights are accorded
b : the status of one who has attained this age
3 a : a number greater than half of a total
b : the excess of a majority over the remainder of the total : MARGIN
c : the preponderant quantity or share
4 : the group or political party whose votes preponderate
5 : the military office, rank, or commission of a major
- majority adjective
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[Bart:] We commonly use definition 3a, but check out 3c above.
Also, the phrase 'majority rule' seems fairly recent. Interesting that
the authors felt that the term 'usually' was necessary:
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Main Entry: majority rule
Function: noun
Date: 1893
: a political principle providing that a majority usually constituted
by fifty percent plus one of an organized group will have the power to
make decisions binding upon the whole
