The Collaborative International Dictionary of English v.0.48:

Magna Carta \Mag"na Car"ta\, Magna Charta \Mag"na Char"ta\ [L.,
   great charter.]
   1. The great Charter, so called, obtained by the English
      barons from King John, A. D. 1215. This name is also given
      to the charter granted to the people of England in the
      ninth year of Henry III., and confirmed by Edward I.
      [1913 Webster]

   2. Hence, a fundamental constitution which guaranties rights
      and privileges.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Magna Charta
    n 1: the royal charter of political rights given to rebellious
         English barons by King John in 1215 [syn: Magna Carta,
         Magna Charta, The Great Charter]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

MAGNA CHARTA. The great charter. The name of an instrument granted by King
John, June 19, 1215, which secured to the English people many liberties
which had before been invaded, and provided against many abuses which before
rendered liberty a mere name.
     2. It is divided into thirty-eight chapters,: 1. To the which relate as
follows, namely: freedom of the church and ecclesiastical persons. 2. To the
nobility, knights' service, &c. 3. Heirs and their being in ward. 4.
Guardians for heirs within age, who are to commit no waste. 5. To the land
and other property of heirs, and the delivery of them up when the heirs are
of age. 6. The marriage of heirs. 7. Dower of women in the lands of their
husbands. 8. Sheriffs and their bailiffs. 9. To the ancient liberties of
London and other cities. 10. To distress for rent. 11. The court of common
pleas, which is to be located. 12. The assize on disseisin of lands. 13.
Assizes of darein presentments, brought by ecclesiastics. 14. The amercement
of a freeman for a fault. 15. The making of bridges by towns. 16. Provisions
for repairing sea banks and sewers. 17. Forbids sheriffs and coroners to
hold pleas of the crown. 18. Prefers the king's debt when the debtor dies
insolvent. 19. To the purveyance of the king's house. 20. To the
castleguard. 21. To the manner of taking property for public use. 22. To the
lands of felons, which the king is to have for a year and a day, and
afterwards the lord of the fee. 23. To weirs which are to be put down in
rivers. 24. To the writ of praecipe in capite for lords against tenants
offering wrong, &c. 25. To measures. 26. To inquisitions of life and member,
which are to be granted freely. 27. To knights' service and other ancient
tenures. 28. To accusations, which must be under oath. 29. To the freedom of
the subject. No freeman shall be disseised of his freehold, imprisoned and
condemned, but by judgment of his peers, or by the law of the land. 30. To
merchant strangers, who are to be civilly treated. 31. To escheats. 32. To
the power of selling land by a freeman, which is limited. 33. To patrons of
abbeys, &c. 34. To the right of a woman to appeal for the death of her
husband. 35. To the time of holding courts. 36. To mortmain. 37. To escuage
and subsidy. 88. Confirms every article of the charter. See a copy of Magna
Charta in 1 Laws of South Carolina; edited by Judge Cooper, p. 78. In the
Penny Magazine for the year 1833, page 229, there is a copy of the original
seal of King John, affixed to this instrument, and a specimen of a facsimile
of the writing of Magna Charta, beginning at the passage, Nullus liber homo
capietur vel imprisonetur, &c. A copy of both may be found in the Magazin
Pittoresque, for the year 1834, p. 52, 53. Vide 4 Bl. Com. 423.