olive branch , n :
A branch of an olive tree offered as an emblem of peace. (figuratively) Any symbol of peace, or a peace offering to an adversary to show goodwill and in the hope of securing peace. […] Today is designated by the United Nations as the International Day of Peace, which is dedicated to world peace.
Source http://handbookblogger.blogspot.com/2017/09/olive-branch-word-of-day-for-september.html
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