IPA: /ˈspaɪn.ləs.li/
KK: /ˈspɪn.ləs.li/
In a way that shows a lack of courage or determination; acting without firmness or strength of character.
He spinelessly agreed to their demands without putting up any resistance.
Spinelessly → It is formed from "spineless" (from "spine" (from Latin *spina*, meaning thorn or spine) and the suffix "-less" (meaning without)) and "-ly" (meaning in a manner of). The word "spinelessly" describes acting in a manner that is without spine, or metaphorically, lacking courage or determination.
Think of someone who is 'without' ('-less') a 'spine' ('spina') — this helps you remember that 'spinelessly' means acting without courage.