tell on
     v 1: give away information about somebody; "he told on his
          classmate who had cheated on the exam" syn: denounce,
           betray, give away, rat, grass, shit, shop,
          snitch, stag
     2: produce an affect or strain on somebody; "each step told on
        his tired legs"
see also:
denounce betray give away rat grass shit 
shop snitch stag 

39 moby thesaurus words for "tell on":
   babble, be indiscreet, be unguarded, bear witness against, betray,
   betray a confidence, blab, blabber, blow the whistle, blurt,
   blurt out, fink, give away, inform, inform against, inform on,
   leak, let drop, let fall, let slip, narc, peach, rat,
   reveal a secret, sell out, sing, snitch, snitch on, spill,
   spill the beans, squeal, stool, talk, tattle, tattle on,
   tell secrets, tell tales, testify against, turn informer