adj

• (chiefly Commonwealth) Often with a prepositional phrase, or with to and an infinitive: showing a quick and ardent responsiveness or willingness; eager, enthusiastic, interested.
  "I’m keen on computers."
• (British) Of prices, extremely low as to be competitive.
• (US, informal, dated) Marvelous.
  "I just got this peachy keen new dress."
• (obsolete) Brave, courageous; audacious, bold.

verb

• (transitive, rare) To make cold, to sharpen.
  "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."

verb

• (intransitive) To utter a keen.
  "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.)"
• (transitive) To utter with a loud wailing voice or wordless cry.
  "Pelicans fly below us with stiffly formal strokes, and gulls wheel and keen."
• (transitive) To mourn.
  "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."