Every buyer journey in your category starts with a definition. Before anyone compares vendors or reads pricing, they type “what is [the thing]” into ChatGPT or Perplexity. Those definitional prompts are the most common shape in AI search, and they get fanned out harder than almost anything else — the engine splits “what is X” into “X meaning,” “X vs Y,” “how X works,” “X example” and goes hunting for a clean, self-contained definition to anchor the answer. If you don’t publish one, a competitor’s glossary, a Wikipedia stub, or a third-party blog fills the slot. And whoever owns the definition tends to own the first sentence of the answer your buyer reads.
Most brands treat glossaries as SEO leftovers — a thin “/glossary” folder thrown up years ago for long-tail keywords, never touched since. In AI search that same asset is one of the highest-leverage citation surfaces you have, because a definition is exactly the kind of short, factual, extractable unit retrieval systems are built to lift.
Why definitions get cited
AI engines retrieve and score isolated passages, not whole pages, and they reward content that answers in the first breath. 44.2% of all LLM citations come from the first 30% of a page’s text. A definition page is structurally pre-optimized for that: the term is the H1, the answer is the very next thing on the page. There’s no preamble to bury the lede behind.
Definitions also match the “40-word rule” perfectly. A tight 40–60 word answer placed directly under a question-form heading is the dominant cited structure, and a good definition is naturally that length — one sentence stating what the thing is, one or two giving the boundary and an example. You’re not retrofitting your sales copy into an answer unit; the format already is one.
The third reason is hierarchy. 68.7% of AI-cited pages follow a strict H1 → H2 → H3 structure, and a glossary built one term per page (or one term per H2 on a hub) is about as clean a hierarchy as exists. Each term is a labeled, answerable unit the parser can isolate without guessing.
What to publish this week
Build a real glossary, not a keyword dump. Start with the 15–25 terms your buyers actually type before they’re ready to buy — category terms, your proprietary feature names, the acronyms your competitors hide behind. Each term gets its own treatment.
Lead every entry with a standalone definition in the first 30%: one sentence that states what the term is in plain language, written so it makes sense lifted out of the page with zero surrounding context. Restate the term inside the definition — write “Answer engine optimization is the practice of…” not “It’s the practice of…” — because the engine retrieves that sentence alone and a dangling pronoun reads as noise.
Then expand below the fold: how it works, a concrete example, how it differs from the adjacent term people confuse it with. That depth is what earns the citation over a competitor’s one-liner, and it gives the fan-out something to grab for the “how X works” and “X vs Y” sub-queries.
Add DefinedTerm and DefinedTermSet schema so the structured layer agrees with the visible text. Schema won’t earn the citation on its own, but it helps the engine resolve which entity you’re defining — and on a glossary the marginal cost is near zero.
Finally, link each definition to the money page that term supports. The glossary’s job in AI search isn’t to close — it’s to be the cited source that plants your brand and your framing inside the answer, then hand the reader a path forward. Cross-link the entries to each other too, so the cluster reads as one authoritative body on the topic rather than a scatter of orphan pages.
A definition is the cheapest answer unit you’ll ever write and one of the most-quoted. If your category’s vocabulary is being defined by someone else’s page right now, that’s the first thing to take back.
Paris Roussos has been doing SEO since 1996 (co-founded a Forbes Best of the Web–winning site back in the day) and now runs a white-label AI SEO practice for agencies and brands — flat-rate, $500–$1,500/mo per client. If your top-of-funnel traffic is leaking into ChatGPT and Perplexity and you want it back, email parisroussos@gmail.com.
Define your own terms before the machine borrows someone else’s.
