For example when you stop doing one thing before it's finished, and start something else because you, or someone else, considers it more important than the thing you were doing. The thing you was doing is now less important than this new thing that needs doing.
I am trying to think of a heading for list of things like this, things have been dropped half way through to start something else "more important", but still need finishing at some point.
De-prioritised is not the correct word for this in my opinion, as you can de-prioritise jobs that haven't yet been started, or may never be started. I am after a word that clearly gets across that I was in the middle of a job that is now sitting half done because I started something "more important".