5-axis machining in CNC processing refers to a machine's ability to move a tool or a part in different axes like three primary axes, X,Y, and Z simultaneously.

What is 5 Axis CNC Machining?   

Multiaxis machining is a manufacturing process that involves tools that move in 4 or more directions and are used to manufacture parts out of metal or other materials by milling away excess material, by water jet cutting or by laser cutting, which is a subtractIve manufacturing process.    
5-axis machines are commonly used in industry in which the workpiece is translated linearly along three axes (typically x, y, and z) and the tooling spindle is capable of rotation about an addition 2 axes.   
The term "5-axis" refers to the number of directions in which the cutting tool can move. On a 5-axis machining center, the cutting tool moves across the X, Y and Z linear axes as well as rotates on the A and B axes to approach the workpiece from any direction.