This is the 3529th most frequent Portuguese word.
plástico
"Plástico" in English means "plastic," referring to a synthetic material made from polymers.
Here, 'plástico' is used as a noun referring to the material the cup is made of.
O copo é feito de plástico.
The cup is made of plastic.
In this case, 'plástica' functions as an adjective, describing the nature of her attitude as lacking depth or authenticity.
Ela tem uma atitude plástica.
She has a superficial attitude.
Here, 'plástica' is used as an adjective in the context of art, relating to the visual qualities and forms.