IPA: /ˈtʃɪə.ləs.li/
KK: /ˈtʃɪr.ləs.li/
In a way that shows sadness or lack of happiness; without joy or cheer.
She walked cheerlessly through the empty streets after the party ended.
Cheerlessly → It is formed from "cheer" (from Old French *chiere*, meaning face or countenance, which later evolved to mean joy or gladness) and "-less" (meaning without). The word "cheerlessly" means without cheer or joy, indicating a lack of happiness or enthusiasm.
Think of 'cheer' as representing joy or happiness, and remember that 'cheerlessly' means lacking that joy.