What word describes something characterized by unusual lightness and delicacy?

The word that describes something characterized by unusual lightness and delicacy is "gossamer." This term often refers to something that is extremely thin, light, and almost ethereal, like the delicate threads spun by spiders or the light fabrics used in certain garments. In a broader sense, "gossamer" can denote anything that is fleeting or subtly beautiful, evoking a sense of fragility and grace.

In the context of the options presented, "excoriate" refers to criticizing severely, "harrow" relates to causing distress or torment, and "hermetic" describes something that is sealed off or impervious, often referencing airtight seals. These definitions do not align with the sense of lightness and delicacy that "gossamer" conveys, making it the most fitting choice for the question.