A mature cheddar head is someone who is very mature but acts really stubborn and stuck-up with it, quite snobby. They are mature in a really boring way with no sense of humour and take everything seriously.
'Sophie told me making fart noises is immature.'
'Don't worry, she's a mature cheddar head with no sense of humour.'
'Don't worry, she's a mature cheddar head with no sense of humour.'
by mousey1306 March 7, 2012