A reset of an inherited asset's cost basis to its value at the owner's death.
When you inherit an asset, its cost basis is generally "stepped up" to the market value on the date of the original owner's death. This can erase the capital gains that built up during their lifetime, so heirs who sell soon after owe little or no capital gains tax. It is a major reason some highly appreciated assets are held rather than sold late in life.
Inherited stock that doubled in the owner's lifetime can be sold by an heir with little capital gains tax.