Stock is a setting in Versus Mode in which the winner is the last player with remaining lives. In stock setting, the game allocates to each player a number of lives, which are depleted one by one each time the player is sent off the stage. If you put a time limit into a stock match via additional rules, when time is up, the winner is the player with the most stock left.
The word "stock" can also be used to describe each life: "We played with 4 stock." Stock setting with a time control is the standard setting for tournaments. It can also be used to indicate how much a player beat another, i.e. Ay says "I 4-stocked Bee" if Ay had 4 stock when he removed Bee's last life.
Stock are used to measure how many times a player can die before they are ejected from the game, though in one player modes, they can Continue at the cost of some Coins and half their Points. They are measured by symbols directly above the player's Damage Percent. Lives can be set to anything from 1 to 99 in vs. matches and from 1 to 5 in Classic and Adventure modes. All-Star must be played with only one life. The player, in Classic or All-Star mode, is given point bonuses depending on whether or not all of their lives remained intact by the end of the last round. The player is also given one life to complete a target mini game, Board the Platforms, Snag the Trophy or Race to the Finish. Despite this, losing will not deduct a life from the next round's total.
JV X-Stocked
Another variation of this is called the JV X-Stock, which is when one player finishes off a person with 1-4 stock remaining but has 0% on that stock, thereby adding one stock to the total and calling it a "JV 2-5-stock." This terminology stems from the idea that if the player hadn't taken that one hit that killed him/her when he/she was at high percentage, the player would have won the battle with one extra stock. The term was created by the player JV, who used to call his 0% finishing wins a JV X-stock, where X represented the value of the remaining stock plus 1.