Valmiki Ramayana Yuddha Kanda Sarga 97 Shloka 27

पतितः dropped, सःकपिः that monkey, समुत्थायgetting up, अशनेःthunderbolt, समानम् equal to, तलप्रहारम् slapped with palm, भीमनिःस्वनम् terrific sound, तस्य his, व्यसर्जयत् crash

Dropped down by him (Virupaksha), Sugriva, got up, and gave the Rakshasa a slap with his palm which was equal to thunderbolt that produced a terrific sound like crash.