Plain English Meaning

Weather that is just barely good enough to fly by looking outside. It legally counts as visual flying conditions, but it's close to the edge — a small worsening can put the pilot into clouds or low visibility they aren't trained or equipped to handle.

Full Definition

Weather conditions that technically meet the legal minimums for visual meteorological conditions (VMC) but only barely — typically with low ceilings, reduced visibility, or both — making safe visual flight difficult and significantly increasing the risk of inadvertent entry into instrument meteorological conditions (IMC).