WordNet records no synonym and no antonym for offing. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the near or foreseeable future
“there was a wedding in the offing”
the part of the sea that can be seen from the shore and is beyond the anchoring area
“there was a ship in the offing”
Synonyms, antonyms and the broader and narrower relations for offing come from Princeton University’s WordNet. Full sources and licences.