Dictionary of Computer and Internet Terms: leading (pronounced "ledding")
leading (pronounced "ledding")
the insertion of extra space between lines of type. On old printing presses, this was originally done by inserting strips of lead between rows of type cast in lead.
In some cases, it is actually beneficial to use negative leading-for instance, when setting type in all caps, it is not necessary to allow space for descenders. Such headlines usually look best with negative leading.
THESE LINES ARE TYPESET
WITH NEGATIVE LEADING.