arb noun 3verb 1forms 4 noun3 •The act of or potential for arbitrage. •One who engages in arbitrage; an arbitrageur. •(informal) An arboretum.Just don't be too scared when you hear rumors of sacrificial ceremonies in the Arb […] — 2005 verb1 •To engage in arbitrage. formsarbed · arbing · arbs · ARBs