Phlegmatic (adjective) — هادئ وبطيء الانفعال: Calm and not easily excited. Below are 8 words with a similar meaning; the linked ones have full GL Dictionary entries with their meaning in Arabic.
Peaceful; tranquil; serene; composed; quiet; still; undisturbed
Calm and showing little emotion.
Calm and not easily upset.
Calm, self-possessed, and poised — composed names the still state, not compose (to write), not compose-yourself (calm down now), and not composed-of (made of…
unexcitableplacidstoicaleven-tempered