unlight
To extinguish, turn off, or dim the light from
rare, transitive
His father, in another room, unlights the lamp and leaves the world alone.
Where it comes from
From un- + light or, in the case of the verb, perhaps from Middle English *unlighten (suggested by past participle unlight, unlyght, unliȝt (“unlit”)), equivalent to un- + light.
Adapted from the Wiktionary entry unlight (CC BY-SA 4.0).