compass plant noun alsocompass flower : any of several plants whose leaves or branches are arranged on the axis so as to indicate the cardinal points of the compass: as a.: a rosinweed (Silphium laciniatum) b.: a prickly lettuce (Lactuca scariola) c.: prairie bird's-foot trefoil d.: a low tufted white-woolly yellow-flowered composite herb (Wyethia ovata) of California