IPA: /ˈplɛntɪəsli/
KK: /ˈplɛntɪslɪ/
In a way that is abundant or plentiful; in large amounts.
The garden produced fruits plenteously this year, providing enough for everyone.
Plenteously → It is formed from "plent" (from Old French *plenté*, meaning fullness or abundance) and the suffix "-ously" (meaning in a manner characterized by). The word "plenteously" means in a manner characterized by abundance or fullness.
Think of 'plent' which relates to abundance, and remember that 'plenteously' means doing something in an abundant way.