Slide is a slur used to describe Blacks in a derogatory way. Used by some police. It was created so that they could refer to blacks in a derrogatory way and not get in trouble. Said because blacks 'slide' through everything - they're lazy. Also said, "part of the White Castle family" ('sliders').
The word Slide is a racial slur that has been used historically to degrade and dehumanize blacks. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to blacks. If you are unsure about whether or not it is appropriate to use the word Slide, it is best to err on the side of caution and avoid using it in any situation.