The Collaborative International Dictionary of English v.0.48:

Sederunt \Se*de"runt\, n. [L., they sat, fr. sedere to sit.]
   A sitting, as of a court or other body.
   [1913 Webster]

         'T is pity we have not Burns's own account of that long
         sederunt.                                --Prof.
                                                  Wilson.
   [1913 Webster]

   Acts of sederunt (Scots Law), ordinances of the Court of
      Session for the ordering of processes and expediting of
      justice. --Bell.
      [1913 Webster]