When all of a player's holdings have been trumped by other players and the player has no longer a secure base to play from, he is said to be "knidded". This can have serious effects - it is not possible to play the move of MC, nor to strile
across more than two zones or use [ghost stations]?
as an escape route. Fortunately, it is usually possible to escape quickly by (1) taking posession of a vacant holding (this is rare except early in the game), or (2) overtrumping by expenditure of tokens, if enough can be found.
"Double knid" means that all the holdings are trumped twice and must be similarly overtrumped to escape (and is thus correspondingly more serious later in the game, but not so much.