That's a particular subcase of it, when you know that there's a word for that concept and you've heard it but you can't remember it. But other times it's more like “there should be a word for this”.
But other times it's more like “there should be a word for this”.
However, that's distinct from what gmzamz asked about: occasions when "you do not have the colloquially accepted term" for something.
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