An unholy downpour that inundates everything with fantastic amounts of liquid. Alternatively, something that moves with such force and in such great quantity that it cannot be diverted, avoided, or stopped.
The torrential rain caused massive flooding.

When questioned about her hoe-riffic behavior, her "explanation" was an exquisitely horrid torrential outburst of profanity.
by Tongue-In-Cheek September 2, 2012
A downpour of whinges so massive it can destroy entire cities or if focussed from one person an entire household.
Sorry I disappeared I had to hide from my Mother's Torrential whinge.
by Slayer Silver Wolf March 22, 2011
A lot of water flowing rapidly in copious quantities.
A hurricane can cause torrential rain.
by J.T. Mersmer November 9, 2019