Definitions for "Closed Game"
A position locked by pawns. Such a position tends to lessen the strength of Bishops and other long-range pieces simply because the pawns get in their way. Knights, not being long-range pieces, can jump over other pieces and pawns and thus are very useful in such closed situations. A typical series of opening moves that lead to a closed position is 1.d4 Nf6 2.c4 c5 3.d5 e5 4.Nc3 d6 5.e4, etc.
A game where newcomers or outsiders are barred.
A position with few, if any, pawn trades where pieces are somewhat restricted in their movement.