Ghabn, the root of the word taghabun, literally signifies fraudulently acquiring a thing at less than its market value. In other words, it denotes "cheating," "deceiving," or "defrauding" in buying or selling. In extended use, it may indicate "overreaching," or "overcoming" someone or something in an engagement. When buyers and sellers engage each other in the act of ghabn, it is called taghabun, thus becoming "mutual" cheating or defrauding.
The Quran uses this in its extended sense as one of the names of the Day of Judgment because the believers will, on that Day, "overcome" the disbelievers in attaining Paradise. Therefore, in the great engagement between the faithful and the faithless, the disbelievers will become the ultimate losers. The believers' delight assured perpetually, nonetheless, they themselves also will wish that they had striven harder in life with sacrifice and good deeds, to have earned even higher stations in the Garden.
Al-Khazin in his commentary explains this verse: "The utter loss of the disbelievers will become evident on the Day of Judgment when they are deprived of eternal delight because of their abandonment of faith. Moreover, believers will realize a certain 'loss,' as well, because they will then realize their missed opportunities in life for increased righteous works. It is also said that many of the haughty, the mighty, the rich and the famous - who are deficient in goodness - will come to stunning disillusionment when they find themselves surpassed by the truly righteous and virtuous who were deemed humble in life."
"The Gracious Quran" - Ahmad Zaki Hammad, pp. 271, 272