an attempt to break into a password-protected computer or computer system with a software program that successively tries all the words in a large dictionary or other word list.
an attempt by a spammer to obtain a list of valid email addresses by testing possible usernames in combination with a domain name.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for dictionary attack
an attempt to hack into a computer or network by submitting every word in a dictionary as a possible password
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012