Type define ephemeral _ and the _ becomes ephemeral: lasting for a very short time. The dictionary blank pulls a one-line definition into your text without you leaving it.
What you type
Five trigger phrases: define, definition of, meaning of, what does, and what is, leading the sentence your _ ends. The word to look up is picked from the surrounding words after stripping the trigger phrase and filler; the implementation takes the longest remaining word, which is usually the distinctive content word (meaning of catalyst _ looks up catalyst).
Where the data comes from
The free dictionaryapi.dev: no API key, no signup. The blank takes the first definition of the first meaning and truncates it to roughly 100 characters so it stays a one-liner in your text and in the secondary display. Definitions are cached for 24 hours per word, on the reasoning the shipped config states plainly: definitions don't churn.
Read-only by nature
The blank declares itself read-only, and the shipped BLANK.md gives the honest reason: cycling is a no-op because the definition is the definition. There's no second answer to rotate to. The looked-up word is embedded in the output (ephemeral: lasting for a very short time) so the fill stays meaningful once the command span clears.
Failure is visible, not silent: a word the API doesn't know comes back as <word>: not found rather than leaving you wondering whether the blank fired. One caveat worth knowing: the longest-word heuristic means a lookup phrased with an unusually long filler word can occasionally pick the wrong target; rephrasing with a bare define <word> _ is unambiguous.
Related: What is a blank? · The countries blank · Context-aware lookups · GitHub repo