1. to state or declare something firmly and with certainty, without doubt or hesitation
She asserted with confidence that she would win the competition.
Ela afirmou com confiança que ganharia a competição.
2. to express one's opinion or position in a bold and assured manner
He asserted with confidence his position on the matter during the meeting.
Ele afirmou com confiança sua posição sobre o assunto durante a reunião.