99% of discussion of other people is ordinary, good-natured, and harmless.
1%, if that, crosses the line, and it's this we're going to term gossip.
If gossip is damaging in some way, it might be warranted to call up the person one gossiped to and retract the content. Such cases must be dealt with on a case-by-case basis.
In such cases, there is a natural time-limit on retraction, as it's exceptional for the content of gossip to be remembered beyond a few days.
Damaging gossip would be where actual harm has flowed (e.g. from misrepresentation, outright lying, breach of confidence), e.g. in the form of conflict, harm to business interests, damage to reputation, etc. There is also the general harm of the 'bad taste left in the mouth' and the building of relationships on the foundations of unloving thoughts.
Where real harm has been done, which is usually where the gossip has breached its banks and flooded the landscape, direct and overt amends must be made.
Otherwise:
(1) Stop it
(2) If the person is brought up in conversation again, (a) speak well of them or (b) be silent
(3) If gossip is going on around you, quite invisibly redirect conversation to another topic.