What does the underlined word mean in the following sentence and

What does the underlined word mean in the following sentence and what contextual clue is used? “He was in a mood of complete euphoria, his happiness being the result of an announcement that he had won the sweep-stakes.”
【正确答案】：

“EUPHORIA” MEANS (A FEELING OF) HAPPINESS. THE CONTEXT CLUE USED IS SYNONYMY.

【题目解析】：兴奋意味着幸福的感觉。使用的上下文线索是同义词。