We love this word. On the one hand, it means lighthearted, merry, and carefree in disposition or character — a positive, to be sure. On the other hand, it takes on a more negative bent as it can also mean lacking in consideration, heedless, and a little too casual when it comes to thinking things through. Our example sentence uses the latter definition.
Example: In a panic due to her client’s anger over the poor wearing capability of the carpet she specified for his bank lobby, Judith met the manufacturer’s representative at the site to inspect. To her dismay, he reacted with blithe unconcern, even after seeing the product’s deteriorated condition first-hand.