Refers to when you make friendly eye-contact with one or more occupants of a neighboring dwelling, and thus you do not have to actually knock on their door to make it acceptable for you to go on in.
My neighbors down the street have known me for decades and have always welcomed me in to "shoot da breeze for a few"; they often hang out around the dinner-table in their large-glass-windowed kitchen, anyway, and so they can easily notice me as I amble up the front walk. So I always just watch for them to glance up and give me affable nods as I near their glass storm-door; this is my implied door-knock, and so I know that I can just stroll right on in and sit down with them.
by QuacksO July 6, 2018