flat-footed Share definition Flag Flat-footed: Slow, behind the times, stupid, dull, dumb. Not fast enough to "catch up". Jim was caught flat-footed in his response to the question regarding the latest techno gizmo's. flat-footed by Douglas Schmidt June 17, 2008 0 0 Get merch Get the flat-footed mug. Buy Now — $32.95 See more merch