a metaphorical and dimensionless measure of the confusion, ambiguity, or lack of information that characterizes a situation, as in “All the turmoil in the markets means we’ll have a really high fog index around our sales projections”; this jargon superficially resembles a meteorological term but has no real source in that discipline; also evokes the more well-known concept of the “fog of war”; used when the speaker wants to sound technical or sophisticated; see also black box, which similarly hints at bafflement, and a lot of moving parts, which emphasizes complexity