"In spate" is a phrase generally used to describe a sudden and overwhelming surge of water flowing in a river or a stream. However, there are several synonyms that can be used in place of "in spate." Some of them include "flooding," "swollen," "surging," "gushing," "rushing," "torrential," and "rampant." These words are often used to describe the force and intensity of water movements, especially during heavy rainfall or snow melting season. Additionally, they may also be used to describe the overflowing of emotions or events that are occurring in a rapid and intense manner.