Something that is imposed is usually unwelcome and unpleasant and is expected to be endured — like higher taxes or unwelcome guests.
The adjective imposed comes from the Latin imponere, "to place upon, to inflict or deceive." An imposed tax is one placed upon you by law. The English word comes by way of the Middle French verb imposer, meaning "to lay a burden." So if you are imposed upon by an unwanted guest, you'll have to endure an imposed visit.