null

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Having no legal force; invalid: render a contract null and void.
2. adj. Of no consequence, effect, or value; insignificant.
3. adj. Amounting to nothing; absent or nonexistent: a null result.
4. adj. Mathematics Of or relating to a set having no members or to zero magnitude.
5. v. To make null.
6. n. Zero; nothing.
7. n. An instrument reading of zero.

Century Dictionary and Cyclopedia

1. Not any; wanting; non-existent.
2. Void; of no legal or binding force or validity; of no efficacy; invalid.
3. Of no account or significance; having no character or expression; negative.
4. n. Something that has no force or meaning; that which is of a negative or meaningless character; a cipher, literally or figuratively.
5. n. Specifically In musical notation, the character 0, denoting
6. n. in thorough-bass, that the bass note over which it is placed is to be played alone, the other parts resting;
7. n. in the fingering for stringed instruments, that the note over which it is placed is to be played on an open string.
8. n. The raised part in nulling or nulled work. This when small resembles a bead; when longer, a spindle.
9. To annul; deprive of validity; destroy; nullify.
10. To form nulls, or into nulls, as in a lathe. See nulling.
11. To kink: said of a whalemen's line as it runs from the line-tub.
12. Zero in algebraic measure.
13. In math. logic, noting a propositional function when it is false for all values of x.
14. n. Specifically, one of the bids in the game of skat. Same as misère. See skat.

Wiktionary

1. n. A non-existent or empty value or set of values.
2. n. Zero quantity of expressions; nothing.
3. n. computing the ASCII or Unicode character (␀), represented by a zero value, that indicates no character and is sometimes used as a string terminator.
4. n. computing the attribute of an entity that has no valid value.
5. n. One of the beads in nulled work.
6. adj. Having no validity, "null and void"
7. adj. insignificant
8. adj. absent or non-existent
9. adj. mathematics of the null set
10. adj. mathematics of or comprising a value of precisely zero
11. adj. genetics, of a mutation causing a complete loss of gene function, amorphic.
12. v. transitive to nullify

GNU Webster's 1913

1. adj. Of no legal or binding force or validity; of no efficacy; invalid; void; nugatory; useless.
2. adj. Having a value of zero.
3. adj. (Math.) Empty; having no members.
4. adj. (Computers) Unassigned or meaningless; -- a special value given to variables, especially pointers or logical variables, indicating that it is meaningless and cannot be used in computation. The actual value that is stored in memory to indicate the null condition may vary with the computer language used.
5. n. Something that has no force or meaning.
6. n. That which has no value; a cipher; zero.
7. v. obsolete To annul.
8. n. One of the beads in nulled work.

WordNet 3.0

1. n. a quantity of no importance
2. adj. lacking any legal or binding force