The meaning of NULL is having no legal or binding force : invalid. How to use null in a sentence. Did you know?, null is a fundamental concept in many programming languages. It is ubiquitous in all kinds of source code written in these languages. So it is essential to fully grasp the idea of null . We have to understand its semantics and implementation, and we need to know how to use null in our source code., Null definition: without value, effect, consequence, or significance.. See examples of NULL used in a sentence., Define null. null synonyms, null pronunciation, null translation, English dictionary definition of null. adj. 1. Having no legal force; invalid: render a contract null and void. 2. Of no consequence, effect, or value; insignificant. 3. Amounting to nothing;, , .