The noun is derived from mad + cap (“(informal) head”). The adjective is from an attributive use of the noun.
Meanings
Capricious, impulsive, or reckless; also, bizarre, crazy, zany; or foolish, idiotic.
a madcap activity a madcap idea a madcap plan
[T]hose fairy times when I was a mad-cap boy, crowding every enjoyment into the present moment; […] 1808 January 25, [Washington Irving], “Monday, January 25, 1808. From My Elbow-chair.”, in Salmagundi: Or, The Whim-whams and Opinions of Launcelot Langstaff, Esq. and Others, number 20, London: J[ohn] Limbird, […], published 1824, →OCLC, page 137, column 2:
With this shift in both what shows are being made, and in what viewers desire, the genre hearteningly appears to be reverting to its roots of being an entertainment spectacular, giving the space for novelty and mad-cap amusement that's presented in a warm and humorous way. After a discordant patch, it's in tune again – even if some auditionees, as ever, are not. 2021 September 15, Laura Martin, “How Talent Shows Became TV’s Most Bizarre Programmes”, in BBC Online, archived from the original on 22 Jul 2025:
[T]he madcap girl ran up to her mother, put her arms round her waiſt, kiſſed her, tried to make her dance, and ſaid: "Don't be ſilly, you kind little mamma, and cry about Frank turning Papiſt. What a figure he muſt be, with a white ſheet and a candle walking in a proceſſion barefoot!" 1852, William Makepeace Thackeray, “I Go Home, and Harp on the Old String”, in The History of Henry Esmond, Esq. […] , volume III, London: […] Smith, Elder, & Company, […], →OCLC, page 53:
[H]is mad-cap follies, / VVhich ſtill like Hydras heads grovv thicker on him. 1610–1616 (date written), Iohn [i.e., John] Fletcher, Monsieur Thomas. A Comedy. […], London: […] Thomas Harper, for Iohn Waterson, […], published 1639, →OCLC, Act I, scene iii, signature [C4], recto:
O lepidum caput, O mad cap maſter. c. 1588 (date written; published 1591), [John Lyly], Endimion, the Man in the Moone. […], London: […] I[ohn] Charlewood, for the widdowe Broome, →OCLC, Act V, scene ii, signature G, verso:
My madcap plan was to catch that 0456, then hang about – probably for the 0624. 2020 March 25, Steve Roberts, “Parly-vous?”, in Rail, Peterborough, Cambridgeshire: Bauer Media, →ISSN, →OCLC, page 68:
The young Oxonian, on the contrary, had led out one of his maiden aunts, on whom the rogue played a thousand little knaveries with impunity; he was full of practical jokes, and his delight was to tease his aunts and cousins; yet, like all mad-cap youngsters, he was a universal favourite among the women. 1820 January 1, Geoffrey Crayon [pseudonym; Washington Irving], “Christmas Eve”, in The Sketch Book of Geoffrey Crayon, Gent., number V, New York, N.Y.: […] C[ornelius] S. Van Winkle, […], →OCLC, page 389:
The film featured a madcap car chase that went right through a crowded café.
The noun is derived from mad + cap (“(informal) head”). The adjective is from an attributive use of the noun.
Meanings
A person who acts in a capricious, impulsive, or reckless manner.
Come-on you mad-cap: Ile to the Ale-houſe vvith you preſently; […] c. 1590–1591 (date written), William Shakespeare, “The Two Gentlemen of Verona”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act II, scene v], page 27, column 1:
I should like to have seen that noble old madcap Peterborough in his boots (he actually had the audacity to walk about Bath in boots!), with his blue ribbon and stars, and a cabbage under each arm, and a chicken in his hand, which he had been cheapening for his dinner. 1861 November, W[illiam] M[akepeace] Thackeray, “George the First”, in The Four Georges: Sketches of Manners, Morals, Court, and Town Life, London: Smith, Elder and Co., […], →OCLC, pages 34–35:
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; […] 1599, I. Haywarde [i.e., John Hayward], The First Part of the Life and Raigne of King Henrie the IIII. […], London: […] by [Edward Allde and T. Judson for] Iohn Wolfe, […], →OCLC, page 19:
Near-synonyms: mad lad, madlad
Lord, that ſuch a Mad-Cap as I ſhould ever live to be jealous! 1667 March 12 (first performance; Gregorian calendar), John Dryden, Secret-Love, or The Maiden-Queen: […], London: […] Henry Herringman, […], published 1668, →OCLC, Act III, page 34:
(South-Asia) A very foolish or irresponsible person; a fool, an idiot.
[R]un around as he commands. He is a madcap and we must learn to live with him. We are in his hands. 1983, R[asipuram] K[rishnaswami] Narayan[aswami], A Tiger for Malgudi, New Delhi; Navrangpura, Ahmedabad: Allied Publishers [in arrangement with William Heinemann], →OCLC, page 50:
(obsolete, rare) An insane person; a lunatic.
VVhy vvhat a mad-cap hath heauen lent vs here? c. 1596 (date written), William Shakespeare, “The Life and Death of King Iohn”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act I, scene i], page 1, column 2:
Bel[lamont]. […] [W]hat place is this? / May[bery]. Bedlam iſt not? / Bel. VVhere theſe mad-men are, I neuer vvas amongſt them, as you loue me Gentlemen, lets ſee vvhat Greekes are vvithin. / […] / Bell. Pray beſtovv your name ſir vpon vs. / Full. My name is Full-moone. / Bell. You vvell deſerue this office good maiſter Full-moone: and vvhat mad-caps haue you in your houſe. c. 1601 (date written), Thomas Decker [i.e., Thomas Dekker]; Iohn Webster [i.e., John Webster], North-ward Hoe. […], London: […] G[eorge] Eld, published 1607, →OCLC, Act IV, signature F3, recto:
pl ekscentryk (person who acts in a capricious, impulsive, or reckless manner) · ru сумасбро́д (person who acts in a capricious, impulsive, or reckless manner) · bg лудетина (person who acts in a capricious, impulsive, or reckless manner) · pl wariat (person who acts in a capricious, impulsive, or reckless manner) · pl narwaniec (person who acts in a capricious, impulsive, or reckless manner) · pl wariatka (person who acts in a capricious, impulsive, or reckless manner) · pl ekscentryczka (person who acts in a capricious, impulsive, or reckless manner) · fi huimapää (person who acts in a capricious, impulsive, or reckless manner)