its basically the same as conceited..
look at the examples
-Shut your conceited head up
"We didnt want him to get a big head"
-We didnt want him to become conceited
"He's had a big head ever since he won that championship"
-He's been conceited ever since he wont that championship
2. someone who literally has a big head
Shane: "You big headed tit. Your ugly as shit no-one wants you, your a fat ugly shit with moobs"
2. Your heads so big that you cant fit through the door