Onslaught: vicious attack; large number of things We are prepared for the onslaught from entrenched interests in Washington. We expect to prevail. Now is the moment of decisive action. The city faced an onslaught of heavy rain, causing widespread flooding and power outages. The company's customer service team was overwhelmed by an onslaught of complaints following the product recall. The soldiers bravely held their ground against the enemy's onslaught, despite being outnumbered. After the onslaught of negative reviews, the restaurant made several changes to improve its menu and service. The small town was unprepared for the onslaught of tourists during the summer festival, leading to overcrowded streets and long lines.