WordNet records no synonym and no antonym for tinsel. 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.
impart a cheap brightness to
“his tinseled image of Hollywood”
adorn with tinsel
“snow flakes tinseled the trees”
interweave with tinsel
“tinseled velvet”
a showy decoration that is basically valueless
“all the tinsel of self-promotion”
a thread with glittering metal foil attached
Synonyms, antonyms and the broader and narrower relations for tinsel come from Princeton University’s WordNet. Full sources and licences.