Fog \Fog\, v. t. [imp. & p. p. {Fogged}; p. pr. & vb. n. {Fogging}.] 1. To envelop, as with fog; to befog; to overcast; to darken; to obscure. [1913 Webster] 2. (Photog.) To render semiopaque or cloudy, as a negative film, by exposure to stray light, too long an exposure to the developer, etc. [Webster 1913 Suppl.]