This is the 4951st most frequent Spanish word.
durmiendo
Sleeping.
Durmiendo is used here to indicate an action currently in progress in the present continuous tense.
El gato está durmiendo en el sofá.
The cat is sleeping on the sofa.
Durmiendo here describes an ongoing action in the past, serving as a background for another event.
Ayer, mientras estaba durmiendo, escuché un ruido fuerte.
Yesterday, while I was sleeping, I heard a loud noise.
Durmiendo expresses an ongoing action, used here to indicate an improper or unwanted activity while another event should take place.