Light chop
I think this is over used, and ESPECIALLY by Delta pilots. Delta is the butt of many jokes about this, even on the radio when I hear light chop my assumption is it might actually be pretty smooth. Just report smooth, or if you are compelled to say light chop, use a prefix like occasional, or intermittent.
Let's get some accurate variety in turbulence reporting. For goodness sake, Delta prides themselves on being the best, show it by using terminology out of the AIM.
http://www.faraim.org/aim/aim-4-03-14-475.html