Is there a sesquipedalian word meaning "first and maybe last"?

single-word-requests meaning

As in "Welcome to the First And Maybe Last Vernal Equinox Quest". We are having an over-the-top egg hunt-like event at the office, which we may never want to do again. ;)


Solution 1:

Idiosyncratic:

adjective

Relating to idiosyncrasy; peculiar or individual:

ODO

Ultra-idiosyncratic from a film review by Andreas Stoehr:

The experience of Histoire(s) du cinéma is not unlike browsing YouTube—itself a form of algorithm-guided channel-surfing—except here there's an ultra-idiosyncratic auteur presence shepherding you through centuries of high and low culture.

Related

Origin of "deez nuts"
"Not... neither" or "not... nor"
Is there an opposite term for [sic]?
Was the abbreviation "PC" for "Personal computer" in wide use before the IBM PC?
Origin of "How are you?"
Why "paediatrics" but "pedagogue" in British English?
You can apologise *for* something, but can you apologise *that* something?
When did animal sounds get codified?
When the sum of independent Markov chains is a Markov chain?
Prime ideal and nilpotent elements [closed]
Noetherian module implies Noetherian ring?
Showing that there do not exist uncountably many independent, non-constant random variables on $ ([0,1],\mathcal{B},\lambda) $.