Definition of "fitful"

Duncane is in his Graue: / After Lifes fitfull Feuer, he ſleepes well, / Treaſon ha's done his worſt: not Steele, not Poyſon, / Mallice domeſtique, forraine Leuie, nothing, / Can touch him further.

c. 1606 (date written), William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act III, scene ii], page 140, column 2

Harp of the North! that mouldering long hast hung / On the witch-elm that shades Saint Fillan's spring, / And down the fitful breeze thy numbers flung, / Till envious ivy did around thee cling, / Muffling with verdant ringlet every string,— […]

1810, Walter Scott, “Canto I. The Chase.”, in The Lady of the Lake; […], Edinburgh: […] [James Ballantyne and Co.] for John Ballantyne and Co.; London: Longman, Hurst, Rees, and Orme, and William Miller, stanza I, page 3

Like the figures on arras, that gloomily glare / Stirred by the breath of the wintry air, / So seen by the dying lamp's fitful light, / Lifeless, but life-like, and awful to sight; […]

1816 February 13, [Lord Byron], “The Siege of Corinth”, in The Siege of Corinth. A Poem. Parisina. A Poem, London: […] [T[homas] Davison] for John Murray, […], stanza XXI, page 33, lines 575–578

The cabin lamp—taking long swings this way and that— was burning fitfully, and casting fitful shadows upon the old man’s bolted door,—a thin one, with fixed blinds inserted, in place of upper panels.

1851 November 14, Herman Melville, “The Musket”, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley, page 567

So fitful has Britain’s economy been that any good news is understandably snatched at.

2012 October 27, “The economy: Don’t say ‘green shoots’: Britain emerges from its second recession in four years”, in The Economist‎, London: Economist Group, archived from the original on 29 October 2012