The phrase "billboard posters" refers to large signs or advertisements that are displayed outdoors, often along roads or highways, to catch the attention of the public. Full definition
Degreasor In The Province Of Accumulation 5, 2011, bent lacquered steel, phosphate acid, section of billboard poster on «blue back» paper, magnets, 148 x 153 x 30 cm, 58.3 x 60.2 x 12 ins (vilmagold.com)
Re Insomniac secret game: Yeah I'd say Resistance 3 is a fair bet as there have been plenty of «leaks», my favourite being the R3 billboard poster on a movie set (can't remember the time or film). (dealspwn.com)
Drawing inspiration from the immensity of billboard posters in the United States, where Smith has lived and worked since 1959, his works expand the perspective of the canvas itself through the use of dynamic colours and forms. (fadmagazine.com)