This is the 7108th most frequent Japanese word.
リーマン
"リーマン" is a colloquial term in Japanese meaning "salaryman" or a white-collar office worker.
In this sentence, 'リーマン' is short for 'サラリーマン' (salaryman), which refers to a company employee or office worker.
彼はリーマンとして忙しい日々を送っている。
He is living busy days as a salaryman.
Here, 'リーマン' refers to Bernhard Riemann, a mathematician, and is used in the context of mathematical terminology.
リーマン幾何学は数学の一分野である。
Riemannian geometry is a branch of mathematics.
In this context, 'リーマン' refers to Lehman Brothers, the company involved in the financial crisis.