Definitions:

1. Another term for the pound sign (#). NOUN
   • In early telephone systems, the octothorpe symbol was often used for special functions.
2. Name for the symbol #, commonly referred to as the hash or pound sign, used in various contexts, including numbering, social media hashtags, and in computing. NOUN
   • She used the octothorpe in front of her favorite keywords to create trending hashtags.

Synonyms:

• crosshatch
• hash
• number sign
• numeral sign