A Bishop is only consecrated if he isn't already a Bishop. This would normally happen in smaller dioceses, where a Priest is appointed to head the diocese but he of course must be consecrated a Bishop to do so.

In larger dioceses and archdioceses the person appointed to fill the role of diocesan Ordinary is usually a Bishop already. This isn't necessary but it is the norm. In that case he isn't consecrated again and all he has to do is take canonical possession of the diocese.

I think the technical term your asking about is "taking canonical possession of a diocese". The particular ceremony you might be thinking about (when the Apostolic Nuncio and the former Ordinary lead the new Ordinary to his throne) is usually called an installation.

I think it's either a legal term for a bishop becoming head of a diocese or type of church, ie. a basilica?  I've more frequently heard the word used by Anglicans or Episcopalians, especially in the U.S.A.  I know some some primarily black "churches" in the US "install" new pastors and bishops, the A.M.E. in particular.  
The first time I recall hearing the word was when a black colleague of mine was on her church committee to install a new bishop.  I still think it's an odd word to refer to a person taking up a position.  One installs a new refrigerator in the kitchen and a furnace in the basement.  The SSPX installed Bp. Williamson in the attic in Wimbledon, but he made too much noise up there, so they put him out on the sidewalk.