Ball Terminal" src="http://typographydeconstructed.com/wp-content/uploads/2010/12/ball-terminal-white.gif" alt="Ball Terminal" width="190" height="190" />A circular form at the end of the arm in letters.

Ball terminal is a combination of a dot (tail dot) or circular stroke and the curved bit (hook) at the end of some tails and the end of some arms (a, c, f). Beak terminal refers to the sharp spur or beak at the end of a letterform's arm and the curved bit (terminal) between the beak and the arm.

wikipedia Reference

A ball terminal is a design feature of a typeface or glyph where the end of a stroke takes a roughly circular shape, as opposed to a serif or a square end.