Here are some things to know:
It rhymes with the ladies' name "Becky."
The name originates with the word REConnaissanCE.
Reconnaissance - n. - military observation of a region to locate an enemy or ascertain strategic features.
early 19th century: from French, from reconnaître ‘recognize’
A RECCE is a rifle, originating as a reconnaissance rifle built especially for the US Navy SEALs. It is an AR15 with special modifications designed around being both:
A) relatively lightweight and useful for CQB, and
B) being accurate enough to engage targets well beyond 300 meters.
In the end, you get a rifle that can not only hold its own with match competitors out to 600 meters or more; but can also fill the role of high speed, low drag entry weapon.
Here is a picture thread on civilian RECCE clone rifles.
I have one, and it looks like this:
Note: As of August 2015, I've changed my primary rifle to a SPR, which similarly had its roots in the RECCE builds.