Wikipedia
Round-tripping, also known as round-trip transactions or "Lazy Susans", is defined by The Wall Street Journal, as a form of barter that involves a company selling "an unused asset to another company, while at the same time agreeing to buy back the same or similar assets at about the same price." Round trips are characteristic of the New Economy companies. They played a crucial part in temporarily inflating the market capitalization of energy traders such as Enron, CMS Energy, Reliant Energy, and Dynegy.
In international scenarios, round tripping is used for tax evasion and money laundering as well.
Other companies making unconventional round-tripping deals include AOL with Sun Microsystems and Global Crossing with Qwest Communications. It is alleged that when some telecommunications companies swapped capacity, they booked the value of the outgoing capacity as revenue and the value of the incoming capacity as an investment. These transactions had the effect of inflating profits. The SEC ruled that booking revenues from swaps in telecommunications capacity was improper.
Many such companies have used round-tripping to distort the market by establishing false revenue benchmarks, aiming to meet or beat the numbers put out by Wall Street stock analysts. As a result of abusive round trips, barter between publicly held companies has become discredited among professional investors.