This is the verse translation, not a definition of the individual word.
Then He sent down tranquility upon you after distress: a slumber overtaking a group of you[1], while another group[2] cared only about themselves, having false thoughts about Allah, the untrue thoughts of ignorance, saying, “Do we have any say in the matter?” Say, “All matters belong to Allah.” They conceal in their hearts what they do not reveal to you. They say, “If we had any say in the matter, none of us would have been killed here.” Say, “Even if you had been in your homes, those among you who were destined to be killed would have come out to their killing places.” But Allah did this so that He may test your inner thoughts and distinguish what is in your hearts. For Allah is All-Knowing of what is in the hearts.