I just read a post where someone was using the adjective splendiferous and even remarked he would not use that word lightly.
So I did a quick search and found that it has the same meaning as splendid, as well as the same function, i.e. both are adjectives.
What is special about splendiferous in contrast to splendid?
From the Online Etymology Dictionary:
splendiferous (adj.)
considered a playful elaboration since its re-birth in 1843, but it was a perfectly good 15c. word, from Medieval Latin splendorifer, from splendor (see splendor) + ferre "to bear" (see infer).
Thus, it's a valid word with approximately the same meaning and usage as splendid, but it's now considered more fanciful than the simpler word, more appropriate for whimsical or ostentatious contexts.
It appears that splendiferous is a 19th century coinage meant as an intensification of splendid, which is a couple of centuries older.
Since splendid is already a fairly intense word, splendiferous is usually a deliberately florid choice.
It's hard to use splendiferous these days without sounding silly and pretentious. You may find it used seriously in older books (say, 150 years ago or so).
In a very technical sense, "splendiferous" means "bringing or containing splendor" not merely being splendid. Similarly carboniferous means "containing carbon." So a "splendid city" would be a great place in its own right, but a "splendiferous city" would be one that contained multiple splendid things--even if the city itself were ugly. I cannot find any evidence that anyone has ever actually made this distinction, though.
