The adjective inert means someone or something that does not move at all.

Synonyms are dormant, immobile, impotent, or inactive.

The word origins from French (16th century) inerte or directly from Latin inertem meaning “unskilled, incompetent, inactive, helpless, weak, sluggish, worthless”, used of stagnant fluids, uncultivated pastures, expressionless eyes. It is a compound of in– meaning “without, not, opposite of” plus ars meaning “skill”.

Neon is an example of inert gas.

I really don’t like his inert personality.

Their performance today is almost inert. They didn’t impress the audience.