What it means: lacking in interest, vitality, and purpose; listless or lethargic; lazy or indolent, in a dreamy way

From the mid-18th-century interjection lackadaisy, which means “alas, alack” (1748), an alteration of lack-a-day, from alack the day.  Hence, “given to crying ‘lack-a-day,’ vapidly sentimental.” Sense probably altered by influence of lax.

Why I chose it: It’s a such a musical word, for such a dreamy, dreary disposition.