2) (read as Duuuude): you're not gonna believe this!
3) (read as DUUUuud): what you said just really ticked me off.
4) (read as Dude Dude Dude): hot chick at nine o'clock!
*Thanks to Stephan Pastis and Rat
2) How to address someone who's name you don't know
3) Cry of anger or suprise
It slowly is losing it's meaning Just like the word "Like" it is just randomly thrown in to sentances by America's youth.
2) Uh dude I don't know who you are but go away
3) DUDE! you stepped on my toe, ow