Shiny and covered in small, bright decorations, like glitter or sequins.
Spangly things are often seen as fun, flashy, and a little bit showy.
Examples:
Her dress is spangly and sparkly.
The spangly stars in the sky are beautiful.
The spangly shoes are very shiny.
The spangly hat is so bright, it hurts my eyes!
I want a spangly jacket covered in shiny things.
The spangly costume made her look like a star.