Bleh is a word commonly used by ATV users/riders. This word is worldly known as "Would You Like To Go Quadding/Riding/ATVing". People often refer it was Quadding/Atving/Riding. This word has recently been added to the "popular" lingo, and I guess if your cool, you will get others to use this aswell.
Bleh can now be seen as the opposite of blah. something that is hip, cool. stylish, stands out, sweet and not plain boring. Probably the coolest newest use of a word.
If someone yells "bleeeeeh!" as a car drives by, then the car is probably really cool or tricked out. If someone says "i'm wearing all bleh," it means they are wearing cool, hip clothing.
If you don't believe this definition then your probably not all bleeeh anymore. Its like the word "ill", "sick", "gnarly" in that it means sort of the opposite when said the right way. This is the coolest newest use of a word. "The word "bleh" is all Bleeeh!"