Fibber
/ˈfɪbər/
Definition 1 of 1
Pro Tip 1/3Colloquial Usage
Used in casual conversation, not in formal writing or speeches. 
My little brother is a fibber; he makes up stories about space travel.
Pro Tip 2/3Mild Disapproval
Indicates lying in a playful or less serious manner, not heavy moral judgement. 
Oh you fibber, I know you took the last cookie!
Pro Tip 3/3Often for Children
Commonly used to address or talk about children who tell lies. 
Stop being a little fibber and tell me the truth about the broken vase.