For other languages it's a big "it varies", though the second definition seems to be the most common. The term "billion" is honestly, as ambiguous as using "06-03" for a date.
Also note that, historically, English also followed the second definition, so for old literature it's also confusing.
For English-speaking countries, 1B = 1M * 1k
For Spanish-speaking countries, 1B = 1M * 1M
For other languages it's a big "it varies", though the second definition seems to be the most common. The term "billion" is honestly, as ambiguous as using "06-03" for a date.
Also note that, historically, English also followed the second definition, so for old literature it's also confusing.