1. An expression of exasperation, resignation, or rhetorical questioning used when someone has already mentioned multiple things and is asking what more could be added to the list
He complained about the weather, the traffic, and his job. Mais o quê?
Ele reclamou do tempo, do trânsito e do trabalho. Mais o quê?
2. An interjection expressing 'what else could happen' or 'what more is there' in a context of frustration or inevitability
The car broke down, the meeting was cancelled, and now it's raining. Mais o quê?
O carro quebrou, a reunião foi cancelada, e agora está chovendo. Mais o quê?