Nonchalant

adj.calm, capableeveryday

What it means

Calmly confident and free from visible anxiety.

Reach for it when describing outward ease and lack of visible concern

The nonchalant soloist recovered smoothly from a broken string.

playful
cool
stylish confidence and control suit the voice
not when Cool is vague and highly context-dependent.
everyday
casual
informal ease rather than anxiety is meant
not when Casual can also suggest insufficient care.
warm
easygoing
a relaxed disposition is being described
not when Easygoing is broader and more consistently positive.
warm
unruffled
composure survives a disturbance
not when Unruffled does not imply indifference.
professional
composed
controlled behavior under pressure deserves praise
not when Composed may conceal intense concern rather than lack it.
formal
blasé
overfamiliarity has produced indifference
not when Blasé is more jaded and usually negative.
literary
insouciant
light elegant unconcern is the exact shade
not when Insouciant is unfamiliar and can sound affected.

nonchalant manner
His nonchalant manner steadied the nervous rehearsal room.
appear nonchalant
She tried to appear nonchalant while awaiting the result.
nonchalant confidence
Nonchalant confidence carried the solo through a broken string.

Nonchalant can praise composure or criticize indifference; the surrounding consequence determines the tone.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.