At first glance a crab seems to be a very negative dream symbol.
It could represent a “crabby” or unpleasant personality.
The claws could be symbolic of a clinging and hurtful person, or a side of your own personality.
There may be too much dependence, clinging and forcefulness in your life. The crab may also symbolize your inability to effectively move forward and address your own difficulties.
(Remember the crab often moves sideways or backwards.) Some folklore interpretations say that the crab is an omen of poor health.
However, there is a more positive interpretation for the crab in your dream.
In some areas of metaphysics, the crab is a representative of the sea and the sky.
It represents physical nourishment which can be obtained from the sea and also intellectual nourishment.
See also: Animals, Cancer