noun

• (computing) The null character; the ASCII or Unicode character (␀), represented by a zero value, which indicates no character and is sometimes used as a string terminator.
• (computing) The attribute of an entity that has no valid value.
  "Since no date of birth was entered for the patient, his age is null."
• (statistics) The null hypothesis.

adj

• (mathematics) Of the null set.
• (mathematics) Of or comprising a value of precisely zero.
• (genetics, of a mutation) Causing a complete loss of gene function; amorphic.
• (mechanical engineering, of a position or setting) Neutral.
  "In normal operation, the input cranks to both the MPCU and standby rudder actuator will rotate to provide the servo valve command to the units, and the rudder will be hydraulically moved by the MPCU. The rudder movement is in turn fed back mechanically to both the MPCU and standby actuator systems so that when the rudder surface deflects to the position commanded by the pilot, the input cranks on both of the units will be returned to their null positions. Thus, there is a geometric relationship between the rudder position, the input crank of the MPCU, the torque tube, and the input crank of the standby rudder actuator that is retained during normal operation."

verb

• (transitive, archaic) To nullify; to annul.
  "Thy fair enchanted cup, and warbling charms / No more on me have pow’r, their force is null’d, / So much of Adders wiſdom I have learnt / To fence my ear againſt thy Sorceries."
• (computing, slang, transitive) To crack; to remove restrictions or limitations in (software).
  "A nulled or a cracked plugin is basically a hacked version of a paid plugin that offers its premium functionalities for free."