The official GemStone IV encyclopedia.
EXTINGUISH is a mechanical verb. It is used to put out flames of items that maybe lit.
Extinguish (lit) item:
>extinguish lantern You snuff the silver lantern, causing the flame to go out. Person snuffs the silver lantern, causing the flame to go out.
Extinguish (unlit) item:
>extinguish lantern Your silver lantern isn't lit.