Idiomatically a four-letter word is a swearword, considered rude and unacceptable in certain contexts.
The implication is here is that thinking and coming up with original solutions to problems is not to be frowned upon in the same way, and indeed is acceptable and encouraged.
To be nothing like means it is completely different and has nothing in common. Nothing like anything means incomparable; completely different from all other things. This is the literal meaning of the term, no figurative or idiom involved.
There are three examples of nothing like anything in the Corpus of Contemporary American English (COCA):
it was just an unbelievable event and nothing like anything the country had ever gone through before
Here the speaker means the event was completely unlike any event previously experienced in the country.
" It seems like I've always had some type of adversity, " Bobby says. " My freshman year at Duke, we lost the title game by 30 to UNLV.... But this is big adversity, nothing like anything else. # "
Here the speaker is referring to some type of adversity that this time has a magnitude never before seen, incomparable to any previous adversity.
" She spun around, drinking in the scenery, marveling at its almost palpable presence. " But... this is nothing like anything I've ever seen on the' net! "
Here, whatever it is the speaker is experiencing is unlike any experience she has had in the same environment.
Best Answer
2×4:
Image courtesy of Wikipedia.
Edit: Wikipedia has since corrected itself that this is indeed a 2×6, but you get the idea.
Oh, and the sentence as a whole means that the observation was a big surprise or a great shock; an aha experience or a eureka moment; an eye-opener.