praseodymium(n = noun.substance)atomic number 59, pr - a soft yellowish-white trivalent metallic element of the rare earth group; can be recovered from bastnasite or monazite by an ion-exchange process;
An elementary substance, one of the constituents of didymium; -- so called from the green color of its salts. Symbol Ps. Atomic weight 143.6. [1913 Webster]