Frivolous (adjective)

1. Not serious or sensible; trivial.
2. Lacking a sense of responsibility or seriousness.

Origin:

From latin "frivola" meaning trifling, unimportant, or worthless.

Examples:

1. The court found the lawsuit to be frivolous and dismissed it.
2. The proposal was deemed frivolous and was not taken into consideration.
3. He had a frivolous attitude and was always cracking jokes, even in serious situations.
4. The party was filled with frivolous guests who were more interested in having a good time than discussing serious matters.
5. The criticism was deemed frivolous and was not taken into consideration by the team.