Definition of yestreen in English:

yestreen

Pronunciation /jɛˈstriːn/

adverb

poetic Scottish
  • On or during the evening of yesterday; last night. Also occasionally more broadly: yesterday.

noun

poetic Scottish
  • The evening of yesterday. Now somewhat rare.

Origin

Late 15th century; earliest use found in Liber Pluscardensis. Scots variant of yester-even.