I know that *Word up!* is a versatile expression and its meaning depends on different regions. But in a movie I came across this expression as in:

> 
> A: Hey, there's this big banquet for my university nomination, wanna come?  
> 
>  B: No, I have something to do.  
> 
>  A: There's an open bar there.  
> 
>  B: Word up! 
> 
> 
> 

I guess it's an enthusiastic exclamation but I'm not sure.  

Isn't it like saying *Sweet!* or *Hot dog!* when we express enthusiasm?