trifle with (someone or something)
To treat or deal with someone or something in a frivolous or disrespectful manner. Often used in passive constructions. You can't just go through life trifling with people and their affections without any regard for their wellbeing. I wouldn't do that if I were you—the plans of the boss are not to be trifled with.
trifle with someone or something
to act without seriousness or respect toward someone or something. Don't talk that way to me! I am not to be trifled with. I wish that Ann wouldn't trifle with our efforts at reform.
trifle with
v. To play or toy with someone or something: Don't trifle with my affections. My strict boss is not someone to be trifled with.