The Collaborative International Dictionary of English v.0.48:

Taleteller \Tale"tell`er\, n.
   One who tells tales or stories, especially in a mischievous
   or officious manner; a talebearer; a telltale; a tattler.
   [1913 Webster]

WordNet (r) 3.0 (2006):

taleteller
    n 1: someone who gossips indiscreetly [syn: tattletale,
         tattler, taleteller, talebearer, telltale,
         blabbermouth]