A man (or person) who displays large amounts of sass, generally in a feminine or queer manner with large amounts of self confidence. This is usually characterized by stance, quips, and other not so subtle-subtle mannerisms.
There are many possible scenarios where one may exhibit symptoms of Sassy Man Syndrome, and SMS (Sassy Man Syndrome) is not a joke, so it is important to be aware of these signs so you can seek the help necessary for those with SMS /j
Some of these examples are;
Example A
man: *says something super sassy with a smug ass look*
person: that guy has a serious case of Sassy Man Syndrome
Example B
man: *sits with a manspread*
person: I think he has a case of Sassy Man Syndrome