The phrase "fog in" is typically used to describe a situation where visibility is reduced due to a thick fog. However, there are several other synonyms for this phrase that can be used to describe similar situations. For example, "fogged up" can be used to describe a window that has become obscured by condensation or fog. "Misty" or "hazy" can be used to describe a more subtle reduction in visibility, often caused by humidity. Additionally, "smoggy" can be used to describe a situation where air pollution has combined with natural fog to create a hazardous mix. Regardless of the specific word used, it's important to take caution when navigating in reduced visibility situations to avoid accidents.