Cylindrical: Refers to the standard cylindrical shape of the handle of a cutting tool, used for clamping by a chuck.
Blade shape: Although called a "column knife", its cutting part usually has a taper and is not a column of the same thickness as the top and bottom. A more accurate description would be 'conical flat bottomed knife'.
Its main features are:
The blade is straight (unlike a helical milling cutter) with a certain degree of taper.
The bottom edge (tip) is flat and usually "center cutting", which can cut vertically like a drill bit.
The side blade has a slight angle with the axis, forming a taper.
