litter on a stick n. roadside billboards, signs, and advertisements. (source: Double-Tongued Dictionary)
Further reading
A Charlotte, North Carolina, shares her granddaughter’s adorable misunderstanding of a word. When a breeze was blowing, the little girl would say it’s winding (rhyming more or less with “wending” rather than...
For one family in Oklahoma City, Oklahoma, the expression tuna casserole serves as code for “Tonight’s dinner doesn’t sound so good, so let’s go out to eat.” This is part of a complete episode.
Related
Smaller signs are referred to here (http://www.causs.org/) as street spam, vertical litter, bandit signs, snipe signs, utility pole advertising, stuff on a stick