To dream of crabs, indicates that you will have many complicated affairs, for the solving of which you will be forced to exert the soundest judgment. This dream portends to lovers a long and difficult courtship. ... Ten Thousand Dream Interpretation
Catching crabs in a dream indicates a complicated state of affairs in a courtship or in matrimony, though not necessarily beyond hope of solution. Eating crabs is an indication that selfishness is likely to get you into difficulties. Seeing them displayed for sale predicts that a mystery will shortly cause you great concern.... The Complete Dream Book
Symbol: The crab symbolizes resurrection, since it renews/ changes its protective shell regularly.
Vision: Looking at one or more crabs: your plans are delayed (one step forward—three steps back) and it will take time to get back on track.
If you or others are eating crabs: your financial situation will improve. Having cancer: somebody wants to destroy your livelihood—expose this as quickly as possible!
Depth Psychology: This animal is a sign that some of your personality traits are in conflict with your values and/or the environment. Seeing a crab in your dreams often means you are too accommodating.
If you dream that you have cancer, it is important to know where the cancer is located (the head, neck, chest, stomach, etc.).... Dreamers Dictionary