low, deciduous shrub (Purshia tridentata) of the family Rosaceae (rose family), widely distributed in the W United States where it is a characteristic constituent of the vegetation on arid slopes and desert ranges. One of the most important Western browse plants, it provides abundant forage throughout the year for both cattle and deer. Antelope brush is classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Rosaceae.