What's the word?

What's the word for when you get an ice cream headache? It's on the tip of my tongue...

Fact is: the technical term for an ice cream headache, is: "Ice Cream Headache."

And psychology's accepted technical term for having a word on the tip of your tongue is: "Tip of the Tongue Phenomenon."

Very interersting.... I'm now wondering if there are any other strings of words that we commonly use for which there is no single-word replacement.

I'm also wondering why there is no word for "a string of words for which there is no single-word replacement". The only dictionary word I can find that defines "a string of words for which there is no single-word replacement" is "Figure of Speech." But that's not quite it...

What's the word for "something for which there is no word."