to take (something/somebody) seriously: to give (something/somebody) your attention, to think (something/somebody) is important or valuable idiom Luna is disappointed that no one takes her suggestions seriously. She really needs to feel like her ideas are important.

The police have to take any terrorist threat seriously. You don't take anything seriously, do you? It's all one big joke to you. She's sick of being seen as a sex symbol and wants to be taken seriously as an actress. These young actors take themselves so seriously!