Antagonym? Contranym? Janus word?
Unbeknownst to many, there are two pretty odd quirks of the English language out there that happen to be my favourites for reasons that may seem nonsensical. Unfortunately, they often go overlooked. I just used three examples:
Unbeknownst (meaning not many people know about it) and nonsensical (meaning something that doesn’t make sense) are lovely examples of Unpaired words. These are words with prefixes such as un- and non-, but where the word doesn’t really exist without the prefix. In this case, we never say “beknownst” or “sensical”. It seems like these words should have a paired (related) word… but they don’t.
And that’s nice.
But you know what else is nice?
Antagonyms (also called contranyms or Janus words) are words that have two meanings that happen to be the opposite of each other. A classic example is cleave, which means either “to split something (for example when chopping wood with an axe)” OR “to stick to something”.
So it’s technically reasonable to say “he cleaved the log into two pieces, then cleaved them back together.”
And that’s why nonplussed is my favourite word in the English language. It’s an unpaired word (there is no such word as plussed) that means:
Surprised, confused, unsure how to react, shocked into non-reaction
Unfazed, unperturbed, not bothered by something.
It’s honestly a good thing that there is no such word as Plussed. Who knows what it would even mean?