MEF meaning in General ?

Maximum elevation figure (MEF) is a type of visual flight rule (VFR) information that indicates the elevation of the highest geographical feature within a GEOREF quadrangle area. It is of interest to pilots, who want to be aware of the highest mountain peaks and tall towers nearby, so that they can fly above them to avoid controlled flight into terrain. ("Features" includes terrain, trees, towers, and other obstacles.)

Unlike the minimum safe altitude (MSA) used for flight under instrument flight rules, the MEF does not include any margin for aircraft clearance above the terrain nor for aircraft altimeter error.

In a VFR flight, the MEF is commonly referred to as a "quadrantal altitude" (not to be confused with an IFR minimum sector altitude).