Your final answer(s) should be thematic.
perimeteris there... and it's a "definition" for the word
rim, which is inside it. Surely, that must be relevant?
And if you line up the red frame, you can see it perfectly covers the word "rim".
The word "limit", though... it doesn't have a nice substring that it defines. But it is written strangely...
...and if we look carefully, we can see the word CAP!
So, now to continue this with the rest!
It starts to get trickier from here:
And some even weirder things happen...
The next two are entirely based on the font's design, not really using the individual letters:
...the next one is in whitespace...
... and the last one is in hanzi! Online translators give "thermal" for
熱的, and indeed we can find HOT inside it.
But there's still one more thing: