1. In a manner without foundation, basis, or justification; without valid reason or evidence
He groundlessly accused her of theft without any evidence.
Ele a acusou infundadamente de roubo sem qualquer prova.
2. In an unsupported or unsubstantiated way; based on nothing concrete
The rumor was groundlessly spread throughout the community.
O rumor foi infundadamente espalhado por toda a comunidade.