You know, when a record is meant to be seamless and fade from one track into another.
Seem to remember the Soulwax record having lots of this (and even a secret track if you had a certain sort of CD player). Mansun Six is one of my favourite for flicking from one song to the next. But on iTunes, unless you set it up properly, there's often a second or so which ruins the flow.
Related... Spotify have just added a new thing so that you can listen to albums gaplessly... http://www.spotify.com/uk/blog/archives/2012/02/23/spotify-now-with-gapless-playback-crossfade/