Synonymous for saying someone is one hell of a smart monkey.
Ex 1:
John: Well I’ll be a monkey's uncle! Steve Jobs has made Apple more valuable than Microsoft on the market!

Justin: There's no doubt he's a shrewd simian.

Ex 2:
I just saved a lot of money by switching to GEICO! Call me pretentious, but this car owner feels like one shrewd simian!
by ShrewdSimian June 4, 2010
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