Definition of "keen"

Ophe[lia] You are keene my Lord, you are keene. / Ham[let] It would coſt you a groaning, to take off my edge.

c. 1599–1602, William Shakespeare, “The Tragedie of Hamlet, Prince of Denmarke”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies, London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, act III, scene ii, page 268, column 2

In fact, she doesn't mention the fact that I've obviously been avoiding her, just sounds genuinely thrilled to hear from me, and as soon as I mention getting together she suggests Monday, which is rather keen, even for Portia.

2000, Jane Green, Bookends, London: Penguin Books; republished as Bookends: A Novel, trade paperback edition, New York, N.Y.: Broadway Books, 2003, page 304

[N]euer did I know / A creature that did beare the ſhape of man / So keene and greedy to confound a man.

c. 1596–1598, William Shakespeare, “The Merchant of Venice”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies, London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, act III, scene ii, page 176, column 1

The tongues of mocking wenches are as keen As is the Razors edge, inuisible: […]

c. 1595–1596, William Shakespeare, “Loues Labour’s Lost”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies, London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, act V, scene ii, page 139, column 1

Come thick Night, / And pall thee in the dunneſt ſmoake of Hell, / That my keene Knife ſee not the Wound it makes, / Nor Heauen peepe through the Blanket of the darke, / To cry, hold, hold.

c. 1606, William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies, London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, act I, scene v, page 134, column 2

For when we rage, aduiſe is often ſeene By blunting vs to make our wits more keene.

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

So, when remote futurity is brought / Before the keen inquiry of her thought, / A terrible sagacity informs / The poet's heart; […]

1781 January, William Cowper, “Table Talk”, in Poems, 4th edition, London: Printed for J. Johnson, No. 72, St. Paul's Church Yard, published 1782, page 11, lines 492–495

O lawfull let it be / That I have roome with Rome to curſe a while, / Good Father Cardinall, cry thou Amen / To my keene curſes; for without my wrong / There is no tongue hath power to curſe him right.

c. 1606, William Shakespeare, “The Life and Death of King Iohn”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies, London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, act III, scene i, page 9, column 2

Chearful at morn he wakes from ſhort repoſe, / Breaſts the keen air, and carolls as he goes; […]

1764 December 19 (indicated as 1765), Oliver Goldsmith, The Traveller, or a Prospect of Society. A Poem. Inscribed to the Rev. Henry Goldsmith, London: Printed for J[ohn] Newbery; 3rd edition, London: Printed for J. Newbury,[sic – meaning Newbery] in St. Paul's Church-yard, 1765, page 10

Well our hosts here attacked us with a fantastic Dismodulating Anti Phase stun ray and then invited us to this amazingly keen meal by way of making it up to us.

1985, Douglas Adams, The Original Hitchhiker Radio Scripts, New York, N.Y.: Harmony Books, page 82

This is the pureſt exerciſe of health, / The kind refreſher of the ſummer-heats; / Nor, when cold Winter keens the brightening flood, / Would I weak-ſhivering linger on the brink.

1730, James Thomson, “Autumn”, in The Seasons, London: […] A[ndrew] Millar, and sold by Thomas Cadell, […], published 1768, page 93, lines 1256–1259

[S]he went so swiftly that he could only follow her to the door. The large shape of the car swallowed her up; and the car twisted softly around the little drive and away to the London road. Minutes later he heard its Klaxon, just one sharp keen, like the harsh cry of a sea-bird.

1922, Michael Arlen, “3/5/1”, in “Piracy”: A Romantic Chronicle of These Days, London: W[illiam] Collins Sons & Co.

Last night he had put down too much Potheen / (A vulgar blend of Methyl and Benzene) / That, at some Wake, he might the better keen. / (Keen—meaning 'brisk'? Nay, here the Language warps: / 'Tis singing bawdy Ballads to a Corpse.)

20th century, Stuart Howard-Jones (1904–1974), “Hibernia”, in Kingsley Amis, comp., The New Oxford Book of English Light Verse, New York, N.Y.: Oxford University Press, 1978, page 243

Satiran, lost in his own grief, shuddered once, then lifted his head to the sky and keened out his loss to the heavens.

2000, Mercedes Lackey, Brightly Burning, New York, N.Y.: DAW Books

I keened my Gran, I keened my babies, but then my words poured out of my grief. I don't have the full heart like that for Owen, sorry as I am for his goin. Without the heavy grief on me I can maybe think of the words easier.

1996, Virginia Warner Brodine, Seed of the Fire, New York, N.Y.: International Publishers, page 28

She sniffed and nodded and cried and wailed and keened for her husband, who would never come back to her.

2017, Neil Gaiman, Norse Mythology, Bloomsbury Publishing, page 113