Brit., Informal a ballpoint pen
Origin of birofrom Biro, a trademark for a kind of ballpoint pen
- A BIRO brand ballpoint pen.
- (by extension, UK, Australia, New Zealand) Any ballpoint pen.
- (by extension) Ink from a ballpoint pen.
From the BIRO brand of pens made by the BIC corporation, which were named after László Bíró, the inventor of the pen.