Squaring off is a trading style used by investors/traders mostly in day trading, in which a trader buys or sells a particular quantity of an asset (mostly stocks) and later in the day reverses the transaction, in the hope of earning a profit (price difference net of broker charges and tax).

For example, Person A buys 100 shares of Reliance from the BSE Sensex through a broker for a price of Rs 10 per share. Later in the day, Person A sells all the shares for Rs 12 per share and by paying broker charges of Rs 10. The net profit A earns is Rs (200-10)=Rs 190.

Therefore, the trader has basically squared off his position.