No, that doesn’t cover the whole meaning.
How about “the shotgun approach”? I nearly busted my brain trying to find a concise Spanish translation for that once.
Actually, there is a pretty good word in English that covers it - sufficient. Lagom is always used to communicate ‘just enough’, or ‘hits the spot’. It’s when the glass is neither half full or half empty, but just right.
But I got the impression that the OP was thinking more of phrases, not words.
A favourite is “Cat got your tongue?”, which I once saw translated on a subtitle as: “Har katten tagit din tunga?”, i.e. word for word. We have a frase meaning just that in Swedish: i]“Har du inte mål i mun?”* which would be “Don’t you have language in your mouth.”
So yeah, there are a lot of phrases that don’t translate very well. Doesn’t mean there aren’t corresponding phrases.
“Procrastinate” is a tricky one. I fell in love with the English language when I discovered this amazingly useful (for me) word. 
My English to Japanese dictionary gives three Japanese translations which mean “to be lazy”, “to be slow” and “to postpone.” None of these words conveys the full meaning.
There’s no word for “subtle” in Hebrew, a fact which should surprise nobody who’s ever met an Israeli.
I once had to try to explain to a German-born French teacher the slang use of the word “suck”. I had used it in the sentence “We [America] make the whole world suck.” When he gave me a blank look, I found myself utterly unable to explain what it meant. “Umm it means we make the world … lame? Umm, worse? No, that’s not it …” I don’t know if there’s really a direct equivalent in other languages.
If I may return to the wonderful world of films and (un)translatable puns I raise my hat for the genius that came up with the Swedish title for the film That Sinking Feeling by Bill Forsyth. For those, who haven’ät seen it, it’s a delightful comedy about a gang of teenagers in Glasgow, that start a career of hardened criminality by stealing a lorryload of kitchen sinks (diskho in Swedish).
So what title do you give it in Swedish? The answer is of course Diskhofeber, a play with the original title and Disco Fever.
Nothing sucks like an Elctrolux!
There’s no word in Russian for “efficiency.” The closest I’ve ever found is “effectiveness.”
I remember reading about an editor who had trouble translating the phrase “take care” from English into Russian without it sounding like the character was warning about some imminent danger.
Point taken. I suspect that finding a phrase that exists solely in English, to the exclusion of all other languages, would be quite a chore.
To better answer the OP, I should have restricted my contribution to the Portuguese language (and probably Spanish, but I’m not as familiar with that language).
I’m English and used to work in a London office with several French cow-orkers who all spoke more or less fluent English. I once used the word ‘naff’, and the Frenchies asked me what it meant, and it was really hard to explain.
I would venture that all of Yiddish is not quite translatable 
… at least, it’s so effective in its own right that we’ve never bothered to find equivalents for words like “chutzpah.”
Care to repeat the process for us 'Merkins?
And now you’ve got the 'Mercans asking what it meant, too. 
I was using the phrase “to blend in” in German (“einblenden”) until somebody pointed out to me that it did not exist at all.
I did not believe it at first but it is true and I don’t think we even have an equivalent for it…
Well, effektivnost’ kinda covers both meanings, and when you’re translating it’s often a pain having to decide whether the author had “efficiency” or “effectiveness” in mind (this comes up a lot in consultants’ reports, where they’re always nattering on about how their proposed solutions will make something or other more effektivny…).
My suggestion for an English word that has no exact translation - at least into French German or Russian, the only foreign languages I’m reasonably familiar with - is “silly”. The nearest equivalents in other languages are much more in the sense of stupid, idiotic, foolish, but none have the flavor of real montypythonesque silliness…
I’ve tried to explain this to Russian friends and usually get remarks about “subtle English humour”.
Einmon would assimilation work there?
The main reason I find that Swedes object to any suggestions for translations of the word “lagom”, is because it describes not an amount per se, but in fact a swedish existential concept. For the rest of us “just right” works as a translation, but few swedes would agree I feel 
MrsIteki nearly burst a gasket when I suggested “sufficient”
One can eat enough (sufficiant) without having eaten “lagom”.
'Nother ‘Merican here wonderin’ 'bout “naff.”
“Naff” a little similar to the Australian “daggy”. “Naff” can mean goofy, unfashionable, silly, cheesy, awkward… Actually, it is hard to explain exactly.
Anything from an 80s haircut to a poorly done, garishly coloured modification to a “riceboy” car could be described as naff.