Quote in Context
O, beware, my lord, of jealousy;
It is the green-eyed monster which doth mock
The meat it feeds on.
Othello (5.2), Othello
We are all familiar with the above quote, as it is one of Shakespeare's most famous. But what exactly is the green-eyed monster? It seems every editor has a different take on this passage, with many trying to make the lines work around the concept of green as sickly. Some editors have even changed mock to make in order to fit their annotations - Hanmer and Hudson being the most famous. Others have listed off surprising candidates for the monster, including a dragonfly and an ape. It all becomes a bit silly and would no doubt give Shakespeare himself a good chuckle.
It seems very simply that Shakespeare was imagining a cat (known for its giant green eyes), delighting in tormenting (mocking) its victim (meat) before devouring it. What a vivid picture this interpretation gives us of jealousy, tormenting the mind of the jealous man with a barrage of suspicions before it consumes him completely. A similar vision was in the poet's mind when he constructed The Rape of Lucrece:
Yet, foul night-waking cat, he doth but dally,
While in his hold-fast foot the weak mouse panteth:
Her sad behavior feeds his vulture folly. (254-256)