Definition of "muse"

My toung-tide Muſe in manners holds her ſtill,While comments of your praiſe richly compil'd,Reſerue their Character with goulden quill,And precious phraſe by all the Muſes fil’d.

1609, William Shakespeare, “Sonnet 85”, in Shake-speares Sonnets. […], London: By G[eorge] Eld for T[homas] T[horpe] and are to be sold by William Aspley

So may some gentle Muse With lucky words favour my destined urn

1637, John Milton, “Lycidas”, in Poems of Mr. John Milton, […], London: […] Ruth Raworth for Humphrey Mosely, […], published 1646

Come, then, expressive Silence, muse his praise.

c. 1726, James Thomson, Hymn

It is tempting to speculate about the incentives or compulsions that might explain why anyone would take to the skies in [the] basket [of a balloon]: […]; […]; or perhaps to muse on the irrelevance of the borders that separate nation states and keep people from understanding their shared environment.

2013 June 7, David Simpson, “Fantasy of navigation”, in The Guardian Weekly, volume 188, number 26, page 36

Muse not that I thus suddenly proceed; for what I will, I will, and there an end.

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, [Act I, scene iii]

still he sate long time astonished / As in great muse, ne word to creature spake.

1590, Edmund Spenser, “Book I, Canto XII”, in The Faerie Queene. […], London: […] [John Wolfe] for William Ponsonbie

And with this Alan fell into a muse, and for a long time sate[sic] very sad and silent.

1886 May 1 – July 31, Robert Louis Stevenson, Kidnapped, being Memoirs of the Adventures of David Balfour in the Year 1751: […], London, Paris: Cassell & Company, published 1886

He fell into a muse and pulled his upper lip.

1978, Lawrence Durrell, Livia, Faber & Faber 1992 (Avignon Quintet), p. 416