IPA: /ˈθraɪvər/
KK: /ˈθraɪvər/
A person who is successful and grows or develops well in their life or work.
She is a thriver, always finding ways to improve and succeed in her career.
Thriver is formed from "thrive" (from Old Norse "þrifa", meaning to grasp or to thrive) and "-er" (meaning a person who). A thriver is a person who thrives or flourishes in their environment.
Think of someone who is 'grasping' or 'flourishing' in life — that's what a thriver does.