Phlegmatic
/flɛɡˈmætɪk/
noun
One who has a phlegmatic disposition.
adjective
Not easily excited to action or passion; calm; sluggish.
Abounding in phlegm.
“a phlegmatic constitution”
Generating, causing, or full of phlegm.
Synonyms: apathetic, cold-blooded, sluggish, stoic, unflappable