Hi folk! This phrase is an extract from a famous Indian author's book : " India, with its billion-strong population, its modest place on the tally "so, can you give a meaning of ( billion-strong) ?Thanks in advance.
The suffix "-strong" is not uncommon when applied to numbers of people. It really just means "of the specified number". Another example: "five-strong team", a team of five people.
It probably literally means "having the strength of X persons [or things]" (where X is the number), but is used generally as described above. It can also be used of things like ships, often in a military sense.