The term 'kind of pen' can refer to a variety of different types of pens. The crossword solutions for this term include 'POISON' (6 letters), 'BALLPOINT' (9 letters), 'BALL' (4 letters), 'GEL' (3 letters), 'STATE' (5 letters), and 'BULL' (4 letters). POISON pens are pens that contain a toxic ink, which is usually used for writing secret messages. BALLPOINT pens are the most common type of pen, with a small rotating BALL at the tip that dispenses ink. BALL pens are similar to BALLPOINT pens, but they use a thicker ink that is more difficult to erase. GEL pens use a water-based GEL ink that is available in a variety of colors. STATE pens are fountain pens that have a reservoir of ink that is fed to the nib through a feeder. BULL pens are a type of felt-tip pen that uses a thick, porous tip to create bold lines.