s_to

s_to is a direction property given to rooms. When a player types, “GO SOUTH”, DoGo checks that value to see if there is another room in that direction.

room twistypassage "A Maze of Twisty Passage"
{
    long_desc
        "You are in a maze of twisty passage. There is one exit to the south."
    s_to twistypassage2
}

It is aliased by the ignore_response property.