A "yo mama" joke is a reference to a person's mother through the use of phrases such as "your mother" or other regional variants, frequently used to insult the target by way of their mother. Used as an insult, "your mother..." preys on widespread sentiments of parental respect, making the insult particularly and globally offensive. "Your mother" can be combined with most types of insults, although suggestions of promiscuity and/or obesity are particularly common. Insults based on height, hairiness, laziness, incest, age, race, poverty, poor hygiene, unattractiveness, homosexuality, or stupidity may also be used. Compared to other types of insults, "your mother" insults are especially likely to incite violence. Slang variants such as "yo mama", "yo momma", "yer ma", "yer mum", "ya mum", "ya mom", "ur mom", "your mum", "ur mum", "ur mother", "Joe mama", or "your mom" are sometimes used, depending on the local dialect. Insults involving "your mother" are commonly used when playing the Dozens.

Although the phrase has a long history of including a description portion, such as the old "your mother wears combat boots", the phrase "yo mama" by itself, without any qualifiers, has become commonly used as an all-purpose insult or an expression of defiance.