WordNet (r) 3.0 (2006):

hold forth
    v 1: talk at length and formally about a topic; "The speaker
         dissertated about the social politics in 18th century
         England" [syn: hold forth, discourse, dissertate]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "hold forth":
   debate, declaim, demagogue, discourse, elocute, explain, exposit,
   expound, extend, harangue, hold out, lecture, monologize,
   monopolize the conversation, moralize, mouth, offer, orate,
   out-herod Herod, perorate, point a moral, preach, prefer, present,
   proffer, put up, rabble-rouse, rant, read, read a lesson, recite,
   rodomontade, say aside, sermonize, soliloquize, spiel, spout,
   submit, tender, think aloud, think out loud, tub-thump