Darkness: This is the most direct opposite of glimmer, which refers to a faint light.
Dimness: Similar to darkness, but implies a lack of brightness rather than complete absence of light.
Obscurity: This suggests a lack of clarity or visibility, which could be due to darkness or other factors.
Dullness: This refers to a lack of brilliance or excitement, which could be applied to a glimmering light that is faint or uninspiring.
Absence: This is a general antonym for "glimmer," implying that something is completely lacking, including a faint light or a hint of something.
Extinction: This suggests that something, including a glimmer, has completely ceased to exist.
The best antonym for "glimmer" will depend on the specific context of your sentence.