Adjective

(en adjective)

Inactive, at rest, quiet.

The bats were quiescent at that time of day, so we slowly entered the cave.

* Professor Wilson

In times of national security, the feeling of patriotism is so quiescent that it seems hardly to exist.

(grammar) Not sounded; silent.

The k is quiescent in "knight" and "know".

Adjective

(en adjective)

Not easily excited to action or passion; calm; sluggish.

* {{quote-book

, year=1873 , author=Jules Verne , title=Around the World in 80 Days , chapter=2 citation , passage=Calm and phlegmatic , with a clear eye, Mr. Fogg seemed a perfect type of that English composure which Angelica Kauffmann has so skilfully represented on canvas.}}

* 2013 , A.O. Scott, “How It Looks to Think: Watch Her,” Rev. of , dir. by Margarethe von Trotta, New York Times 29 May 2013: C1. Print.

Their friendship (immortalized in a splendid volume of letters that has clearly served as one of Ms. von Trotta's sources) is a fascinating study in cultural and temperamental contrast, an impulsive and witty American paired with a steady, phlegmatic German.

(archaic) Abounding in phlegm; as, phlegmatic humors; a phlegmatic constitution.

Generating, causing, or full of phlegm.

* Sir Thomas Browne

cold and phlegmatic habitations

Watery (en).