This is the 1810th most frequent Portuguese word.
mau
Bad; evil.
In this sentence, 'mau' qualifies 'pressentimento', referring to a negative or ominous feeling.
Ele teve um mau pressentimento sobre a situação.
He had a bad feeling about the situation.
Here, 'mau' refers to the poor quality or improper manner in which the text was written.
Um texto mau escrito pode ser difícil de entender.
A poorly written text can be hard to understand.
The word 'mau' is an adjective used here to describe the quality of the student's ability in mathematics, indicating it is poor.