fimbriation

You know how the Union Jack has those thin white borders on either side of each of the red stripes?

Turns out there's a word for that: fimbriation, adding thin stripes of color around an element of a flag or heraldic device, usually either to set off the element more clearly from its background or to satisfy a heraldic rule about not putting certain kinds of colors next to each other.

The flag of Trinidad and Tobago is a particularly dramatic example of fimbriation. Note that the white stripes here have a specific symbolic meaning ("The white stands for the sea by which the land is bound," says Wikipedia), so they're not just there for visual-design reasons.

When I was a kid, I was briefly big into heraldry; in retrospect, I think a lot of that was being fascinated by the formality and unusual words of heraldic language. (But I don't think I ever encountered the term "fimbriation" during that period.) That Trinidad and Tobago flag, for example, can be described as "Gules, a bend Sable fimbriated Argent." Which translates (more or less) to "On a red background, a diagonal black stripe (running from upper left to lower right if you're facing the flag) with thin white stripes on either side." As with any technical jargon, it can be pretty compact.

It occurs to me that what I ought to have done is written an entry on heraldic language and used "fimbriation" as an example. But that would've taken more time and research than I have time for right now, so I'll leave it at this.