To be good, in a state of being good, to be having a good time.
(See Firefly)
How are you today?
Shiny.
Cool.
(interjection) cool, nifty, awesome, pretty, amazing, wonderful, great, remarkable... etc.
"Hey, what do you think of my new car?"
"Shiny..."
Something or someone that is good, awesome, wonderful, amazing. (See all other positive synonyms.)
"David Bowie is shiny."
"What is that book like?"
"Shiny"
"How about lunch?"
"Shiny"
This is used to describe something that's very cool
(After seeing Spiderman 2) "That movie was shiny!"
something interesting or distracting, generally used when it deverts attention from a task
This usage comes from the phenomenon of birds (particularly crows) being attracted to shiny objects.
Sarah was going to write her paper, but Myspace looked shiny.
"Wasn't Brian with you?"
"He saw something shiny and wandered off."