cool as a cucumber
imperturbableness
coolness
imperturbability
calm
keep one's pants on
compose
calmness
have one's wits about one
calm down
quieten
equanimous
lull
tranquilize
tranquillise
tranquillize
quiet
still
cucumber
calmen
countenance
self-possession
keep one's knickers on
reposed
settle
sile
keep one's hair on
lown
cool
tranquillizingly
calmative
unfrenzied
bestill
centered
salve
keep one's head
pour oil on troubled waters
hold one's nerve
chill
unfrazzled
composure
unpanicked
placid
peacen
calmish
complacently
halcyon
heropanti
encalm
coolheaded