1- Something unimportant, petty as in <em>they regard window shopping as a </em><em>frivolous</em><em> activity;</em>
2- Something that is not serious,for example: <em>she always has </em><em>frivolous</em><em> remarks about my clothes;</em>
3-<em> A</em>nd<em> </em>it is used in law to state that an argument has no solid basis, for instance: <em>They kept showing</em> <em>some </em><em>frivolous </em><em>pieces of evidence.</em>