Adjective

(en adjective)

Having a loud, mournful sound.

* 1879 , , The Story of a Lie , ch. 1:

[S]how him a refined or powerful face, let him hear a plangent or a penetrating voice . . . and his mind was instantaneously awakened.

* 1919, , Duckworth hardback edition, page 49:

Since mid-day their plangent , disquieting cries had foretold its approach.

* 2013 Sept. 22, Corinna da Fonseca-Wollheim, " Music Review: A Middle East Mourned and Celebrated in Suites," New York Times (retrieved 15 May 2014):

In the lament about the massacre — the work’s second movement — he entered a more urgent register in the high reaches of the cello, but the sense of grief was more plangent than raw, devoid of any real outrage.

(rare) Beating, dashing, as waves.

* 1922 , :

What central sea with plume-plucked midnight strewn,

Plangent to what enormous plenilune

That lifts in silence, hinderless and stark?

Adjective

(en adjective)

Capable of giving out a deep, resonant sound.

* {{quote-book

, year= 1837 , year_published= , author= , by= , title= , url= http://books.google.com/books?id=DfIsAAAAYAAJ&pg=PA162 , original= , chapter= Mercury de Breze , section= , isbn= , edition= , publisher= , location= New York , editor= , volume= 2 , page= 162 , passage= The Oath is redacted ; pronounced aloud by President Bailly, — and indeed in such a sonorous tone, that the cloud of witnesses, even outdoors, hear it, and bellow response to it. }}

Full of sound and rich, as in language or verse.

* Addison

The Italian opera, amidst all the meanness and familiarity of the thoughts, has something beautiful and sonorous in the expression.

* E. Everett

There is nothing of the artificial Johnsonian balance in his style. It is as often marked by a pregnant brevity as by a sonorous amplitude.

Wordy or grandiloquent.