DF
n.— «With all the name-calling that has gone on between recumbent riders and regular cyclists, it’s clear the recumbents have better nicknames.… The regular bike cyclists, on the other hand, call themselves “DF” or “Diamond Frame” cyclists. Or sometimes “Uprights.”» —“Bents and Nonbents” by Jeff Kunerth Orlando Sentinel (Florida) Dec. 10, 2007. (source: Double-Tongued Dictionary)