Junk mail is a term used to describe letters or advertising products which are sent to people who have not asked to receive them. It can also apply to email.
Why does no one send me real letters anymore? All I ever receive is junk mail!
When I checked my email this morning there were 15 items of junk mail advertising all kinds of weird things.
You might also know the phrase junk food. Things which are unhealthy but quick to eat like hamburgers and hot dogs are examples of junk food.
I really need to stop eating so much junk food. I’m 2kg heavier than I was 2 months ago.