in a fog—
1. when there is thick mist or fog:
- This neon light has great penetrating power in a fog.
2. (also: all in a fog) perplexed; at a loss:
- I confess that, until it came to light, I was in a fog.
in fog — = in a fog 1:
- Flying in fog—which may be called “blind flying”—involves difficulties not encountered in clear air.