pin clover n : European weed naturalized in southwestern United States and Mexico having reddish decumbent stems with small fernlike leaves and small deep reddish-lavender flowers followed by slender fruits that stick straight up; often grown for forage [syn: {redstem storksbill}, {alfilaria}, {alfileria}, {filaree}, {filaria}, {clocks}, {pin grass}, {Erodium cicutarium}]