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from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun finance The illegal practice of a stockbroker, when they receive a large client order, placing an order for their own account ahead of the client's, knowing when the client's is placed it will move the market and create a profit for the broker.
• noun finance The illegal practice of placing orders for a security on one's own account in advance of promoting or recommending it.
• noun business Any practice of buying something the value of which is about to increase due to a future purchase by another, especially where the knowledge derives from a fiduciary relationship.