A small well- known bird.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
A small bird of the finch kind.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)
A small insessorial bird that feeds on insects, & c., and is often familiar with man.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
Any of several kinds of small singing birds, having short wings, and a short tail that stands up.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)

Usage examples:

A little bird had been hidden in the feathers on the eagle's back, and when the eagle had gone as high as he could, the wren flew up from his back still higher.
- The Book of Nature Myths by Florence Holbrook
I've made it as fit for me as the nest for the wren
- Three Plays by Padraic Colum
And you will laugh again when you watch Rusty Wren go 'way over to the bank of Black Creek all ready for a party when there really is no party.
- The Tale of Cuffy Bear by Arthur Scott Bailey