Often used in a derogatory sense.
El fruslero siempre habla de cosas sin importancia, sin prestar atención a lo que realmente importa.
The frivolous person always talks about unimportant things, ignoring what really matters.
No quiero parecer un fruslero, pero realmente me gusta la moda extravagante.
I don't want to seem frivolous, but I really like extravagant fashion.