v.

1. switch (a car's headlights) from a higher to a lower beam;
   dip
2. become or make darker;
   darken
   
   • The screen darkened
   • He darkened the colors by adding brown
3. become dim or lusterless
   
   • the lights dimmed and the curtain rose
4. make dim or lusterless
   
   • Time had dimmed the silver
5. make dim by comparison or conceal;
   blind
6. become vague or indistinct;
   blur, slur
   
   • The distinction between the two theories blurred

adj.

1. lacking in light; not bright or harsh;
   subdued
   
   • a dim light beside the bed
   • subdued lights and soft music
2. lacking clarity or distinctness;
   faint, shadowy, vague, wispy
   
   • a dim figure in the distance
   • only a faint recollection
   • shadowy figures in the gloom
   • saw a vague outline of a building through the fog
   • a few wispy memories of childhood
3. made dim or less bright;
   dimmed
   
   • the dimmed houselights brought a hush of anticipation
   • dimmed headlights
   • we like dimmed lights when we have dinner
4. offering little or no hope;
   black, bleak
   
   • the future looked black
   • prospects were bleak
   • Life in the Aran Islands has always been bleak and difficult"- J.M.Synge; "took a dim view of things
5. slow to learn or understand; lacking intellectual acuity;
   dense, dull, dumb, obtuse, slow
   
   • so dense he never understands anything I say to him
   • never met anyone quite so dim
   • although dull at classical learning, at mathematics he was uncommonly quick"- Thackeray; "dumb officials make some really dumb decisions
   • he was either normally stupid or being deliberately obtuse
   • worked with the slow students