Meaning of NULL in English
< programming > A special value used in several languages to represent the thing referred to by an uninitialised pointer.
A special value that may be stored in some database columns to represent an unknown, missing, not applicable, or undefined value. Nulls are treated completely differently from ordinary values when evaluating SQL expressions and there are several SQL constructs for dealing with nulls.
FOLDOC computer English dictionary. Английский словарь по компьютерам FOLDOC. 2012