A cuckold is, quite simply, a man with an unfaithful wife. There are connotations of helplessness and humiliation attributed to the word, implications that the husband is helpless to stop her infidelity, and too cowardly to leave the wife. "Cuckold" appears in older texts as a highly insulting and pejorative term.

Cuckolds are sometimes written of as "wearing the horns of a cuckold" or just "wearing the horns". This goes back to an unsubstantiated reference to a tradition in villages of unknown European location where the community gathers to collectively humiliate a man whose wife gives birth to a child recognizably not his own. This is said to have been a parade where the hapless husband is forced to wear antlers on his head as a symbol of his wife’s infidelity. Whether this actually happened or not is irrelevant to the phrase, which survived. In Italy and Spain, "horns" are a metaphor for suffering the infidelity of a partner, not limited to husbands in modern usage. The gesture of the horned hand, , can be used to insult the cuckold. The Spanish word for a consenting cuckold, cabrón, has such an offensive nuance that it is rarely used with its original meaning, "he-goat ". However, according to the tone and the relation to the addressed, it can be even laudatory.

The history of the word is thought to be related to the Cuckoo bird, who is known to put its eggs in another bird's nest. Some think that this points to another hallmark of the cuckold – the raising of a child that is not his own.

The Chinese term for this translates as "wearing a green hat".

Recent usage

The term has made a resurgence in the late 20th century amongst non-monogamous couples with a dominant female allowed to take on additional partners, and a submissive male who is not. This might be regarded as a subculture within the swinging subculture itself. This differs from the original definition in that these men are voluntarily "cuckolded" by their wives, as part of the husband's sexual fantasy of gaining sexual pleasure from being humiliated by his wife -- indeed, the husband may even be the instigator of this practice, raising questions about who is truly the dominant and who the truly submissive partner. This is a common theme in letters to pornographic magazines. It is unclear how common this phenomenon is in real life as opposed to fantasy.