This is the Arabic word for “genie,” but is used to refer to a large category of supernatural creatures.
It seems to be used more often in a negative context. From Wikipedia:
Jinn are often mentioned together with devils. Both devils and jinn feature in folklore and are held responsible for misfortune, possession and diseases.
(I feel like genies in American fiction are more often benevolent?)
Why I Looked It Up
I remembered the word from a subplot in Neil Gaiman’s American Gods, where a jinn was something to be feared.
I found it again in Cutting for Stone. A nursing student is sent to fetch a physician in an emergency situation:
She ran as if jinn were chasing her…