Definition of "skittish"

All such be like a skittish starting horse, whiche coming ouer a bridge, wil start for a shadowe, or for a stone lying by him, and leapeth ouer on the other side into the water, & drowneth both horse and man.

1557, Roger Edgeworth, Sermons Very Fruitfull, Godly, and Learned, London: Robert Caly, The fiftenth treatice or Sermon

How some men creep in skittish fortune’s hall,Whiles others play the idiots in her eyes!

c. 1602, William Shakespeare, “The Tragedie of Troylus and Cressida”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act III, scene iii]

[…] ’Tis pitifulTo court a grin, when you should wooe a soul;To break a jest, when pity would inspirePathetic exhortation; and t’ addressThe skittish fancy with facetious tales,When sent with God’s commission to the heart.

1785, William Cowper, “Book II. The Time-piece.”, in The Task, a Poem, […], London: […] J[oseph] Johnson; […], page 69

For everybody’s family doctor was remarkably clever, and was understood to have immeasurable skill in the management and training of the most skittish or vicious diseases.

1871–1872, George Eliot [pseudonym; Mary Ann Evans], chapter 15, in Middlemarch […], volumes (please specify |volume=I to IV), Edinburgh, London: William Blackwood and Sons, book (please specify |book=I to VIII)