The Collaborative International Dictionary of English v.0.48:

Dissert \Dis*sert"\, v. i. [L. dissertus, p. p. of disserere;
   dis- + serere to join, connect: cf. F. disserter. See
   Series.]
   To discourse or dispute; to discuss. [R.]
   [1913 Webster]

         We have disserted upon it a little longer than was
         necessary.                               --Jeffrey.
   [1913 Webster]