taddle-tail

a nark; someone who snitches

I saw the girl steal the pizzas, however, I'm not going to be a taddle-tail and tell the boss who did it.

taddle-tail by j9j9 January 29, 2008

taddletale 

one who blabs to the nearest authority figure when the slightest bad thing happens

Mommy! Timmy didn't do his homework!
Oh, Tommy! Don't be such a taddletale!

taddletale by a local citizen February 27, 2005