Nonchalant

Despite her nonchalant air, she is paying close attention to everything you say.

Sami was very nonchalant.

Sami was so nonchalant about it.

His nonchalant glances at the priceless paintings were like spitting in the face of the artists.

My girlfriend's nonchalant blandishments slowly convinced me to start lifting weights and jogging.

Matthew was acting as nonchalant as he could.

Marjorie saw Leonard before he saw her. He was walking with three men—joking, laughing absent-mindedly, while his eyes searched for a face in the crowd. She waited a moment, hidden, suffocated with anticipation, her heart turning over and over, until he said a nonchalant good-bye to his companions, who were pounced upon by eager relatives. Then she crept up behind and put both her hands about his wrist.

We handled the whole frenetic situation with a nonchalant attitude.

On the other hand, to arrive after dusk, when the multitude of garish little public-houses are lit up, giving glimpses of crowded jostling bars and taprooms, is an introduction to a fine city well calculated to affect even the most nonchalant.

[…] The Mexican government's response to the American bombing was admirably laid back. General Enrique Diaz Gonzales and Consul General Raul Michel met with United States officials, who issued apologies and an invitation to come to "the next rocket shoot" at White Sands. The Mexican citizenry was similarly nonchalant. "Bomb Blast Fails to Halt Spring Fiesta," said the El Paso Times headline, noting that "many thought the explosion was a cannon fired for the opening of the fiesta."