To let descend by its own weight, as something suspended; to let down; as, to lower a bucket into a well; to lower a sail or a boat; sometimes, to pull down; as, to lower a flag.(verb)
source: webster1913
To fall; to sink; to grow less; to diminish; to decrease; as, the river lowered as rapidly as it rose.(verb)
source: webster1913
To be dark, gloomy, and threatening, as clouds; to be covered with dark and threatening clouds, as the sky; to show threatening signs of approach, as a tempest.(verb)