telling in WordNet English dictionary

1. informing by words
   telling  apprisal  notification 
   
2. an act of narration
   "he was the hero according to his own relation"; "his endless recounting of the incident eventually became unbearable"
   relation  telling  recounting 
   
3. disclosing information or giving evidence about another
   tattle  singing  telling 
   

1. powerfully persuasive
   "a cogent argument"; "a telling presentation"; "a weighty argument"
   cogent  telling  weighty 
   
2. producing a strong effect
   "gave an impressive performance as Othello"; "a telling gesture"
   impressive  telling 
   
3. disclosing unintentionally
   "a telling smile"; "a telltale panel of lights"; "a telltale patch of oil on the water marked where the boat went down"
   revealing  telling  telltale