The term SKYLINE OBSCURER is composed of two words, 'SKYLINE' and 'obscurer'. SKYLINE refers to the outline of a city or other urban area as seen from a distance. An obscurer is something that makes something else less visible or harder to understand. In this case, the two words together refer to something that makes the SKYLINE of a city less visible. Two common examples of this are SMOG and HAZE, both of which are four-letter words. SMOG is a type of air pollution caused by burning fossil fuels, while HAZE is a type of atmospheric phenomenon caused by dust, smoke, and other pollutants in the air. Both SMOG and HAZE can reduce visibility and make the SKYLINE of a city less visible.