مَرْعَبَةٌ

A frightful قَفْرَة [or desert destitute of herbage and of water]. (K. [In the CK and TA, قَفْزَة is erroneously put for قَفْرَة.])

Also A person's springing, or leaping, [towards another,] and seating himself by the other's side, so as to cause the latter, not being aware, to be frightened. (K. [From its measure, it seems to be a simple subst., not a verbal noun, signifying this action as being A cause of fear.])