the GNU version of the Collaborative International Dictionary of English
adj. Favoring slavery.
The Century Dictionary and Cyclopedia
In United States history, favoring the principles and continuance of the institution of slavery, or opposed to national interference there-with: as, a pro-slavery Whig; pro-slavery resolutions.
Word Usage
"One living park fixture, Richard Kessler, is convinced Olmsted had Lincoln face north to defy proslavery tycoons in Manhattan."