What do you call a person that lies all the time?
A person that eats all the time is called greedy. If you know a person that eats all the time, it's likely they will get fat. If they don't get fat and they eat all the time, then that is just the way they were born. edit- greed is where you want and keep everything for yourself where as if you eat a lot you would be called a glutton
What do you call someone who knows everything about something but when it comes to actually doing it they are rubbish?
It is almost a universal negative. everybody at one time or another tells lies. it is even reflected in the Biblical Commandment which strictly speaking bans False witnesses against thy neighbor) Many types of lies are not that at all. there are white lies, mental reservations, and so on. It can even go from Red to Green in the sense kids might alter details of a movie plot so their folks won"t ban them from…