1. be very unhappy or bored with someone/something
I'm sick and tired of his/her poor behaviour
To be 'sick of' something means to be extremely tired frustrated or exasperated by something. When you are 'sick of' something you are fed up angry or bored with it. You can be 'sick and tired of' something 'sick to the death' of something or 'sick to the back teeth' all of these expressions are interchangeable and informal and used to say that you have had enough.