Quoted from my book HOW TO KNOW A PERSON THROUGH FACE READING? 面相http://www.penangfengshui.com/index.php?pages=info_book_02
The top lip or the upper lip of our mouth represents our passion and the bottom lip of our mouth represents our sexual desires. I noticed that some VVIPs who involved in some sex scandals have very fleshy bottom lip.
A person with a big mouth is a person who has no problem to have food or money. However, if the mouth of a person is big and cannot close firmly when he or she is not talking, this person is likely to be a materialistic person. He or she normally has strong sexual desires and loves to brag. He or she loves to show off and cannot keep secret. Thus, he or she is very open minded and he or she does not like to do things secretly but instead, he or she likes to do things openly and hence it is easy for his or her enemy to know their secret and use it as a weapon to attack him or her. A good mouth should be big when the mouth is opened but it must also be able to close firmly when the person is not speaking.