The word "furbo" in Italian is a word that can have a lot of different meanings.  
It is used to depict someone that is crafty, clever, sharp or astute.  It is also used in a negative manner for someone that is sneaky, not trust-worthy, someone that is willing to deceive you or to trick you.

Masculine / Feminine

In the Italian language, adjectives match the noun they are describing in gender and number.

So for feminine variation, the word would be "furba".

Masculine plural - furbi

Feminine plural - furbe

Example of the use of Furbo in Italian

I read an article today about FIAT motor corporation, based in Turin, a northern city.   They are Italy's number one auto manufacturer.  They became a little "furbi" in one of their marketing tactics.  They somehow figured out when the google car comes around to take pictures for google streets.  Very coincidentally, there just happened to be a picture of a FIAT car when they were photographing the address for the Volkswagon (VW) headquarters in Sweden.  Take a look at the picture below.  This is definitely a good example of the use of furbo in the Italian language.