WordNet records no synonym and no antonym for corporate bond. It is the only member of its synset, 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.
a bond issued by a corporation; carries no claim to ownership and pays no dividends but payments to bondholders have priority over payments to stockholders
“a corporate bond is a safer investment than common stock in the same company”
Synonyms, antonyms and the broader and narrower relations for corporate bond come from Princeton University’s WordNet. Full sources and licences.