One more that eleven; two and ten; twice six; a dozen. [1913 Webster]

1.  The number next following eleven; the sum of ten and two, or of twice six; twelve units or objects; a dozen. [1913 Webster]

2.  A symbol representing twelve units, as 12, or xii. [1913 Webster]

twelve, n. & adj.
--n.
1 one more than eleven; the product of two units and six units.
2 a symbol for this (12, xii, XII).
3 a size etc. denoted by twelve.
4 the time denoted by twelve o'clock (is it twelve yet?).
5 (the Twelve) the twelve apostles.
6 (12) Brit. (of films) classified as suitable for persons of 12 years and over.
--adj. that amount to twelve.

Idiom:
twelve-note (or -tone) Mus. using the twelve chromatic notes of the octave on an equal basis without dependence on a key system.

Etymology:
OE twelf(e) f. Gmc, prob. rel. to TWO

N  five, five, cinque, quint, quincux, six, half-a- dozen, half dozen, seven, eight, nine, three times three, dicker, ten, decade, eleven, twelve, dozen, thirteen, long dozen, baker's dozen, quintuplet, twenty, score, twenty-four, four and twenty, two dozen, twenty-five, five and twenty, quarter of a hundred, forty, two score, fifty, half a hundred, sixty, three score, seventy, three score and ten, eighty, four score, ninety, fourscore and ten, sestiad, hundred, centenary, hecatomb, century, hundredweight, cwt, one hundred and forty-four, gross, thousand, chiliad, millennium, thousand years, grand, myriad, ten thousand, ban, man, ten thousand years, banzai, lac, one hundred thousand, plum, million, thousand million, milliard, billion, trillion, five, quinary, quintuple, fifth, senary, sextuple, sixth, seventh, septuple, octuple, eighth, ninefold, ninth, tenfold, decimal, denary, decuple, tenth, eleventh, duodenary, duodenal, twelfth, in one's 'teens, thirteenth, vicesimal, vigesimal, twentieth, twenty-fourth, vicenary, vicennial, centuple, centuplicate, centennial, centenary, centurial, secular, hundredth, thousandth.

twelve noon, twelve tribes of israel