n
1 bed of earth heated by rotting manure to help plants to grow （用粪肥发酵产生热量的）温床.
2 (fig 比喻) ~ of sth place where sth evil or undesirable is able to develop easily and freely （有利于坏事物滋生发展的）温床
*a hotbed of vice, crime, intrigue, etc 罪恶、犯罪、阴谋活动等的温床.

n
be a hotbed of sth
a place where a lot of a particular type of activity, especially bad or violent activity, happens
　the university was a hotbed of radical protest