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"madcap" is also used as a crossword clue. If that's what you saw, the answer is often loco (4 letters).
Definitions
characterized by undue haste and lack of thought or deliberation
Word origin
The noun is derived from mad + cap (“(informal) head”). The adjective is from an attributive use of the noun.
Used in a sentence
“Near-synonyms: mad lad, madlad”
“Come-on you mad-cap: Ile to the Ale-houſe vvith you preſently; […]”
“There vvas then in preſence, a certaine old Knight, called Sir Hugh Linne, a good ſouldier, but a very mad-cap, & one that liued chiefely vpon the liberalitie of noble men; […]”
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer1 curated clues
01“Wildly impulsive”6 letters
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