(1) A female from an origin of poverty and financial ruin.
(2) A Derogatory word defining a Female without the money to purchase the latest fashion. Usually a Female wearing Thrift store clothing, or clothes bought from a second hand store.
(3) A Female willing to do nearly anything for little cash. Up to and including giving Happy Endings
Man, I need a "Third-World Girl" so's I can have a Happy Ending
Hey, Whose that "Third-World Girl" I saw you with last night?
A person who genuinely and seriously calls out somebody's legitimate complaint as a first world problem as a means of trivialising them and their complaint, usually to obtain a smug sense of moral superiority because of how 'in touch' they are with the 'plight of the underprivileged'.
Dave: "Great, my air conditioner just died in the middle of a heatwave! This sucks."
Twat: "This is such a first world problem. At least you have a house and clothes, and perpetual access to the internet on your smartphone to make these status updates."