the annoying tendency of family groups in stores and other public places to spread out and block access for other shoppers or patrons. seen more often during the holiday shopping seasons, but can occur at any time. EFS can cause unsuspecting people to be forced hard against walls, merchandise displays, etc., or to have to detour around the family group to get at something of interest. similar to groups of aircraft, families often spread into various "vee" formations, echelons, and the dreaded "random EFS," past which nothing can pass, not even light.
this past christmas while shopping at a well-known discount department store, i was accosted by a family of four walking in a row across the aisle. as i was checking out items to purchase, the family came upon me, the dad saying "excuse us," as if i had anyplace else to go. i chose to stand my ground, causing the mom to glare at me and the family to pass me single-file. in this manner i prevented an outbreak of Expanding Family Syndrome.