Rock Spider is a slur used to describe Whites in a derogatory way. Term used by English speaking South Africans to refer to Afrikaners. Would not be suprised if used for black people as well, but definately more commonly used towards other whites.
The word Rock Spider is a racial slur that has been used historically to degrade and dehumanize whites. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to whites. If you are unsure about whether or not it is appropriate to use the word Rock Spider, it is best to err on the side of caution and avoid using it in any situation.