magic word

noun4

1. •
   Any word that has a magical effect when uttered.
2. •
   One of the words please, thank you, or hello.

   • If you learn to use magic words when you are little, it would be easy in your adulthood.
   • What's the magic word?
3. •
   Any word that is considered very significant in a certain situation or context.

   • When someone offers you drugs, the magic word is no.
4. •
   A string of text having some special function or purpose.

   • One of the magic words used in the MediaWiki software is __NOTOC__, which hides the table of contents that would normally be on the page.