■ noun
1》 the purchase of goods or shares by one person or party before the opportunity is offered to others.
↘ historical, chiefly N. Amer. & Austral./NZ the right to purchase public land in this way.
2》 the action of pre-empting or forestalling.
Origin
C17: from med. L. praeemptio(n-) , from praeemere (v.), from prae 'in advance' + emere 'buy'.