fog1

noun

• 1 [mass noun] a thick cloud of tiny water droplets suspended in the atmosphere at or near the earth’s surface which obscures or restricts visibility (to a greater extent than mist; strictly, reducing visibility to below 1 km):the collision occurred in thick fog
• [in singular] an opaque mass of particles in the air:a whirling fog of dust
• Photography cloudiness which obscures the image on a developed negative or print.

• 2 [in singular] a state or cause of perplexity or confusion:the coffee helped clear the fog in my brain

verb (fogs, fogging, fogged)

• 1(with reference to a glass surface) cover or become covered with steam: [with object]:hot steam drifted about her, fogging up the window [no object]:the windscreen was starting to fog up
• Photography make (a film, negative, or print) obscure or cloudy.

• 2bewilder or puzzle:she stared at him, confusion fogging her brain
• make (an idea or situation) difficult to understand:the government has been fogging the issue

• 3spray with an insecticide.