[jonesdc]

Can anyone recommend a good dictionary addon for Firefox?

[Quenz]

Simple, recommended by Firefox [0], has light/dark theme [1], more customizable and pretty but not open source [2]. I've not used these extensively.

  [0] https://addons.mozilla.org/addon/dictionary-anyvhere/
  [1] https://addons.mozilla.org/addon/english-popup-dictionary/
  [2] https://addons.mozilla.org/addon/lumetrium-definer/