C25K Share definition Flag Acronym for "Couch to 5K", the process of changing from a couch potato to a runner capable of completing a 5 kilometer race. I got the C25K app for my iPhone; now I'm on Week 5. C25K by Frankie1969 July 22, 2009 0 0 Get merch Get the C25K mug. Buy Now — $32.95 See more merch
