It means to get rid of or do away with.
There is no one word, the term ususally used is "abolition of slavery", however on an individual basis the freeing of a slave by a master is called "Manumission".
abolish means to get rid of or to do away with
Some synonyms for abolish are cancel, void, destroy, erase, remove, omit, or discontinue.
to get rid of or start over