- The boundary of a body of air, contacting the earth's surface, that has fallen below the dew point and usually contains fog.
- A division in altitude above which fog appears.
1884 June 1, The Overland Monthly, page 596:
- Along the base of the Sierra, back of Pasadena, on eastward back of San Gabriel, past Cucamongo, with its noted vineyards, above Pomona and on beyond San Bernardino, growing warmer as it recedes eastward from the sea, is a belt of foothills above the fog line, facing out toward the noonday sun, looking down across the plains and the hills of the Coast Range upon the warm, southern sea, and yet fanned daily by an ocean breeze that has no harshness.
1895, On the Various Stages of Development of Spermatobium, with Notes on Other Parasitic Sporozoa:
- Along the coast Sequoia sempervirens does not grow above the altitude to which the moist sea air generally rises — the fog-line, as it is often called.
2002, Oz Clarke, Oz Clarke's New Wine Atlas: Wines and Wine Regions of the World:
- Up on the ridges above the valley, way above the fog line at between 400 and 700m (1300 and 2300ft), are some great old Zinfandel vineyards, their origins dating back to the sites that were first planted by Italian immigrants back in the closing decade of the 19th century.
- A line painted on a road (usually bright white) that marks the edge of the legally drivable portion.
2003, Isaiah McKinnon, In the Line of Duty: A Tribute to Fallen Law Enforcement Officers from the State of Michigan:
- As the driver of the vehicle reached into the glove box to obtain the insurance information another westbound vehicle crossed the fog line traveling onto the north shoulder of the roadway.
2006, Truck Accident Litigation, volume 978, page 45:
- The reference line is a straight line that runs the length of the accident site, such as a fog line on a straight road.
2015, Robert L. Habush, Art of Advocacy Series: Cross Examination of Non-Medical Experts:
- And I believe you commented somewhere about how the fog line broke at that point and then picked up on the other side of the entrance ramp.
- (computing) (Can we verify(+) this sense?) The point in the stack descending into a portion of the program where there is no available source code, thus making debugging much more difficult. Most notably, the transition into proprietary code in a closed-source operating system.