- The definition of apex is the highest part of something.
The peak of a mountain is an example of its apex.
nounpl. a·pex·es or a·pi·ces
- The highest point; the vertex: the apex of a triangle; the apex of a hill.
- The highest level or degree that is attained. See Synonyms at summit.
- The usually pointed end of an object; the tip: the apex of a leaf.
Origin of apexLatin.
- (UK, trade union) Association of Professional, Executive, Clerical and Computer Staff.