oak       
noun [ C or U ] uk/əʊk/ us/oʊk/
B2 橡树,栎树;橡木,栎木
a large tree that is common in northern countries, or the hard wood of this tree
  a mighty oak 巨大的橡树 
 The timbers of those old sailing ships were mostly oak. 制造那些老帆船的木料主要是橡木。 
 an oak table/cupboard 橡木桌/橱 
 - More examples
 - The brandy is aged in oak barrels for ten years.
 - They found shelter from the storm under a large oak tree.
 - The oak was two metres in girth.
 - The path goes through an ancient oak wood.
 - The walls of the dining hall were panelled in oak.
 
Idiom  
tall/great oaks from little acorns growidiom  saying 参天巨树萌生于幼籽;合抱之木生于毫末
said about organizations or plans that start off very small or simple and become extremely large or successful