What is Apex?

Legal Definition
The summit or highest point of anything; the top; e. g., in mining law, "apex of a vein." See Larkin v. Upton, 144 U. S. 19, 12 Sup. Ct. 614, 36 I Ed. 330; Stevens v. Williams, 23 Fed. Cas. 40; Duggan v. Davey, 4 Dak. 110, 26 N. W. 887.
See also
-- Black's Law Dictionary