Festive; suited to or characteristic of a festival; joyful and celebratory (archaic or rare).
A direct adaptation from Latin 'festivus,' this form appears occasionally in Early Modern English texts but was largely superseded by the more common 'festive' in standard usage.
'Festivous' is basically what 'festive' was before English speakers decided to streamline it—keeping the Latin flavor but dropping the extra syllable that felt unnecessary.
Complete word intelligence in one call. Free tier — 50 lookups/day.