1. A statement or assertion whose truth, validity, or legitimacy is doubtful or open to dispute
The company made a questionable claim about the product's effectiveness.
A empresa fez uma alegação questionável sobre a eficácia do produto.
2. An assertion that lacks sufficient evidence or credibility to be accepted without further verification
His questionable claim to have invented the device was never proven.
Sua alegação questionável de ter inventado o dispositivo nunca foi comprovada.