This is the 8176th most frequent Polish word.
okłamali
"Okłamali" means "they lied" in English.
In this sentence, 'okłamali' is used to indicate that the subject (they) told a deliberate falsehood to another person.
Oni mnie okłamali, mówiąc, że przyjeżdżają.
They lied to me, claiming that they were coming.
Here, 'okłamali' conveys the action of deception directed at the speaker.
Długo nie mogłam uwierzyć, że mnie okłamali.
For a long time, I couldn't believe that they lied to me.
In this example, 'okłamali' describes the act of lying, specifying the person who was deceived and the context of the falsehood.