I was quoting a single sentence of my mini-essay. "Give them a line" probably doesn't make much sense out of context.
The original context was that a line segment is a degenerate case of a rectangle (one with zero width). You can absolutely say a line segment is a rectangle (albeit a degenerate case of one). However, if your partner really wanted a rectangle for their birthday, and you got them a line segment, they may very well be super-pissed with you, even if you're using the same definition of "line segment" and "rectangle".
If you're not using the same definition, or even if you're simply unsure whether you're using the same definition, then when you get your rectangle-wanting partner a line segment for their birthday, not only would they be pissed with you, but you may also be factually incorrect in your assertion that the line segment is a rectangle for all salient purposes.
xkcd's Up-Goer Five comic gave technical specifications for the Saturn V rocket using only the 1,000 most common words in the English language.
This seemed to me and Briénne to be a really fun exercise, both for tabooing one's words and for communicating difficult concepts to laypeople. So why not make a game out of it? Pick any tough, important, or interesting argument or idea, and use this text editor to try to describe what you have in mind with extremely common words only.
This is challenging, so if you almost succeed and want to share your results, you can mark words where you had to cheat in *italics*. Bonus points if your explanation is actually useful for gaining a deeper understanding of the idea, or for teaching it, in the spirit of Gödel's Second Incompleteness Theorem Explained in Words of One Syllable.
As an example, here's my attempt to capture the five theses using only top-thousand words:
If you make a really strong computer and it is not very nice, you will not go to space today.
Other ideas to start with: agent, akrasia, Bayes' theorem, Bayesianism, CFAR, cognitive bias, consequentialism, deontology, effective altruism, Everett-style ('Many Worlds') interpretations of quantum mechanics, entropy, evolution, the Great Reductionist Thesis, halting problem, humanism, law of nature, LessWrong, logic, mathematics, the measurement problem, MIRI, Newcomb's problem, Newton's laws of motion, optimization, Pascal's wager, philosophy, preference, proof, rationality, religion, science, Shannon information, signaling, the simulation argument, singularity, sociopathy, the supernatural, superposition, time, timeless decision theory, transfinite numbers, Turing machine, utilitarianism, validity and soundness, virtue ethics, VNM-utility