The phrase "seize occasion" means to take advantage of an opportunity or moment of favorable circumstances. There are several synonyms for this phrase that can be used depending on the context of the situation. Some of these synonyms include "grasp opportunity," "take advantage," "make the most of," "seize the moment," "capitalize on," "exploit," "utilize," and "avail oneself of." All of these synonyms suggest a proactive approach to making the most out of a particular opportunity. By actively seeking out and taking advantage of favorable circumstances, individuals or organizations can improve their chances of success and achieve their goals.