Entities release other entities by removing them from their inventory without removing them from the game world. The most common form of releasing is a simple drop, where the released entity relocates itself in the game world near the entity that dropped it. After being released, the entity could be collected by another entity, depending on the state of the entity. Some entities are released when they are used, whereas some are completely removed from the game world.
Strong Example In Diablo, player-controlled entities can release items from their inventory to make room for other items. The released items are relocated in the game world next to the player-controlled entity. The player-controlled entity can re-collect any items it releases.
Weak Example In Doom, the player-controlled entity releases bullets by shooting its weapons. The bullets are used at that point, but the final effect is not known until the bullet collides with another entity. The bullet cannot be re-collected, and is removed from the game world upon collision.
Counter Example In Diablo, player-controlled entities can use potions to regain health or mana. Upon using a potion, the potion is removed from the game world. The potion is not released, as it is not relocated anywhere in the game world.