“The use of electronic messaging systems to send unsolicited messages (spam), especially advertising, as well as sending messages repeatedly on the same site.” (related: phishing — “the attempt to acquire sensitive information such as usernames, passwords, and credit card details (and sometimes, indirectly, money), often for malicious reasons, by masquerading as a trustworthy entity in an electronic communication.”, clickjacking, social engineering)
Source:
Gabriel Weinberg’s Mental Models I Find Repeatedly Useful