A Fyxt RPG Disposable Item is an item that the character will consume, or otherwise use to achieve a temporary effect. These are often potions, herbs, or other things a character will actually ingest to gain some benefit. Disposable Items can also be things like a grenade which is meant to affect enemies. In either case these Disposable Items are used up and destroyed.
For more information see the official Fyxt RPG Page on Disposable Items.