n.a letter that is sent successively to several people
英汉双解大词典
chain letter(chainletters)
1.
N-COUNT（可数名词）
A chain letter is a letter, often with a promise of money, that is sent to several people who send copies on to several more people. Chain letters are illegal in some countries. (在某些国家是非法的)连环信; 一种通常带有金钱方面许诺的信，收信人需要将其再寄给更多的人