Finally. I have found a way to search for songs by looking for search patterns in their lyrics!
Lyrics contain "slavery AND cruel"
Lyrics like "* neighb*r *"
As usual, you can combine this with any other rule in SmartPlaylist.
And as usual, you can copy from the lyrics to paste into mails, messages or notes.
This works only for songs actually stored on the device (it doesn't work for songs in the cloud of iTunes Match). For certain protected songs (DRM) it might also not work.
The lyrics must be stored inside the song (you can do that in iTunes) --- SmartPlaylist will not look up lyrics for you in the internet.