Consignment is the act of consigning, the act of giving over to another person or agent's charge, custody or care any material or goods but retaining legal ownership until the material or goods are sold. That may be done for the purpose of shipping the goods, transferring the goods to auction or intending the goods to be placed on sale in a store (a consignment store).
The verb "consign" means "to send" and therefore the noun "consignment" means "sending goods to another person". In the case of "retail consignment" or "sales consignment" (often just referred to as a "consignment"), goods are sent to the agent for the purpose of sale. The ownership of these goods remains with the sender. The agent sells the goods on behalf of the sender according to instructions. The sender of goods is known as the "consignor" and the agent entrusted with the custody and care of the goods is known as the "consignee".