Wiktionary
n. 1 (context economics English) A decrease in the value of a capital asset 2 (context business finance English) A amount by which the proceeds of the sale of a capital asset by its owner are less than its cost to the owner.
WordNet
n. the amount by which the purchase price of an asset exceeds the selling price; the loss is realized when the asset is sold
Wikipedia
Capital loss is the difference between a lower selling price and a higher purchase price, resulting in a financial loss for the seller. The IRS states that "If your capital losses exceed your capital gains, the excess can be deducted on your tax return". Limits on such deductions apply.
Special wash sale rules apply if the same or substantially similar security is bought, acquired, or optioned within 30 days before or after the sale.
Usage examples of "capital loss".
If the capital value of the original investment has changed during the time you've held it, the act of selling makes you liable for a capital gains tax -- or, conversely, wins you the right to declare a capital loss.
I did point out that with General Stores and the Par-Con deal, his capital loss of 2 is set off against a capital gain of 20 or more.