Properly, a small bead of iridium or other hard metal soldered to the very tip of the pen point. Also popularly used to mean the point itself (although many points, such as italic points, do not have nibs).
the writing point of a pen
The replaceable tip of a WACOM Pen or Airbrush.
The end of the pen used to write with. At one time, a nib itself was called the "pen" and everything else was called the " holder". This was a "left over" from the days of dip pens and is the term is no longer used in that manner. In pen collecting circles, referring to the nib as the point or the tip is pretty much considered criminal behavior & is guaranteed to cause more than just a few harsh looks in your direction.
The nib of the fountain pen is usually made of stainless steel or gold. Gold nibs are tipped with a hard, wear-resistant alloy that typically utilizes metals from the platinum group. Most of the common nibs end in a round point of various sizes (fine, medium, broad). Three different lines of nibs I will show you for example. hooded nib semi-hooded nib free mounted nib
The writing tip of a pen or quill. Sometimes will have a metal reservoir attached above or beneath to hold ink for a longer stroke.
The replaceable tip of the WACOM Pens or Airbrush.
The tip of a pen from which the ink flows.
A detachable metal pen tip resembling a small metal cylinder split lengthwise and flattened and tapered at one end. Metal nibs, available in various widths, are made to be inserted into a wooden or plastic handle for use as a drawing instrument. When goose quills were used for drawing and writing, the end of the quill was carved into a nib with a sharp knife blade.