Literally speaking, a buttress is a part of a building or other structure (like a castle or a dam) that's built up against a wall to give support.
So, figuratively speaking, to buttress something is to provide it with strong, stable support.
Part of speech:
Usually a verb, the transitive kind: "this evidence buttresses their claim."
Sometimes a noun, the countable kind: "Forms of ... debate are essential buttresses of the parliamentary process" (The Guardian).
Other forms: buttresses, buttressed, buttressing
How to use it:
Use "buttress" when you need formality and imagery.
That is, when you're saying that one thing buttresses a second thing, you're suggesting that the first thing is like a vertical support tacked onto the second thing, which you're suggesting resembles a grand building, like a castle or a cathedral, that might otherwise be vulnerable to a collapse or an attack.
Talk about people buttressing things, like claims, cases, and arguments; themes, theories, narratives, and points of view; ideals, principles, and institutions; partnerships, alliances, and relationships; or the security of any group, system, process, industry, economy, etc.
Although it's often people and their words and actions doing the buttressing, you can also say that facts, evidence, money, and other things buttress something on their own.
Or, say that someone buttresses something with facts, evidence, etc.
So far we've used the active voice, saying that "someone or something buttresses something else." We can also flip that around and use the passive voice, saying that "something is buttressed by someone or something else," as in "an opinion buttressed by facts," or "an industry buttressed by government subsidies."
Every now and again, we talk about something buttressing another thing against some harmful force: "a longstanding bias that buttresses their opinion against new evidence and rational argument."
examples: She said the customer had thrown a hamburger at her, a claim buttressed by video footage from the security camera.
"With trepidation, I broke the flawless 'peel' [of the pastry] with my spoon. A thick layer of white chocolate ganache buttressed the delicate outer shell."