This is the 8978th most frequent Portuguese word.
atrasar
"To delay" or "to be late."
In this sentence, 'atrasar' is used transitively to mean 'to delay' something, with the subject being the reason for the delay.
A chuva atrasou o começo do evento.
The rain delayed the start of the event.
The verb 'atrasar' is used here in the past participle form as an adjective, describing the status of the flight being delayed by external factors.
Nosso voo foi atrasado devido ao mau tempo.
Our flight was delayed due to bad weather.
The verb 'atrasar' here is reflexive, indicating that the subject might be delayed or late due to personal action.