Real Dictionary

compass plant in American English
a coarse plant (Silphium laciniatum) of the composite family, with large, bristly leaves and heads of yellow flowers, found on the prairies of central U.S.: the leaves reputedly point in a north-and-south direction
noun: any of various plants having leaves that tend to lie in a plane at right angles to the strongest light, hence usually north and south, esp Silphium laciniatum

compass plant in British English
noun: a tall plant, Silphium laciniatum, of central North America, that has yellow flowers and lower leaves that tend to align themselves at right angles to the strongest light, esp in a north-south plane: family Asteraceae (composites)