A memory wipe was a medical procedure by which selectively memory engrams were removed from an individual's mind, usually by use of drugs.
An early technique, referred to a "wiping", was used on Earth in the early 21st century, using drugs such as meperidine and neo-dopamines. These memory wiping methods were protested during the Mind Control Revolt of the 2040s, and outlawed by the Mind Control Laws. Despite moral qualms, Dr. Elizabeth Dehner used these wiping techniques on the Human participants who had interacted with a pair of Vulcans who had been briefly stranded on Earth in 2045. These methods could not, however, be used on the Vulcans. (TOS novel: Strangers from the Sky)
In 2365, Dr. Katherine Pulaski developed a memory wipe technique which was effective on many humanoid species. (TNG episode: "Pen Pals") However, its effects were proven non-permanent and partially reversible in the case of Sarjenka of Drema IV (CoE eBook: Remembrance of Things Past, Book II) as well as Kurn, son of Mogh, of Qo'noS. (KE novel: A Burning House) Pulaski's technique also had no effect on races such as Mintakans (TNG episode: "Who Watches the Watchers?") and Boraalans. (TNG episode: "Homeward")