He couldn't resist crowing about his perfect score on the test to his friends.

crow 本义是"公鸡啼叫"，引申为"得意洋洋地夸耀"。 crowing 是动词 crow 的现在分词形式，在这里表示"炫耀、自夸"的动作，带有像公鸡打鸣那样得意洋洋的意味。