Definition of chuck it down in English:
British Rain heavily.
- For one thing, it's chucking it down with rain at the moment, so the warm evening sunshine is highly unlikely.
- You'd go out in your shirt sleeves and it would chuck it down with rain, or you'd take your umbrella to work only to lose it on a park bench in the ensuing heatwave.
- Abysmal weather today, it rained all day and absolutely chucked it down as I left work making driving home not much fun.