Oxford Essential Dictionary
middle name
noun
a name that comes between your first name and your family name
Longman Dictionary of Contemporary English
middle name
middle ˈname BrE AmE noun [countable]
1. the name that is between your first name and your family name
2. something is sb’s middle name informal used to say that someone has a personal quality very strongly:
Don’t worry – discretion is my middle name.
Oxford Advanced Learner's Dictionary
middle name
ˌmiddle ˈname noun
a name that comes between your first name and your family name
Idiom: somebody's middle name
Culture:
names [middle name names]
Apart from their surname or last name, most British and American children are given two personal names by their parents, a first name and a middle name. These names are sometimes called Christian names or given names. Some people have only one given name, a few have three or more. Friends and members of a family who are of similar age usually call one another by their first names. In some families young people now also call their aunts and uncles and even their parents by their first names. Outside the family, the expression be on first name terms suggests that the people concerned have a friendly, informal relationship
When writing their name Americans commonly give their first name and their middle initial, e.g. George M Cohan. Both given names are used in full only on formal occasions, e.g. when people get married. In Britain many people sign their name on forms etc. using the initials of both their given names and their surname, e.g. J E Brooks, but may write Joanna Brooks at the end of a letter. The full name (= all given names and surname) is usually only required on official forms.
Parents usually decide on given names for their children before they are born. In some families the oldest boy is given the same name as his father. In the US the word junior or senior, or a number, is added after the name and surname to make it clear which person is being referred to. For example, the son of William Jones Sr (Senior) would be called William Jones Jr (Junior), and his son would be called William Jones III (‚William Jones the third’).
Many popular names come from the Bible, e.g. Jacob, Joshua, Matthew, Mary, Rebecca and Sarah, though this does not imply that the people who choose them are religious. Other people give their children the name of somebody they admire, such as a famous sports personality, or a film or pop star. In Britain the names William and Harry became common again after the sons of Prince Charles were given these names. In the US Chelsea was not a common name for a girl until President Bill Clinton’s daughter Chelsea came to public attention.
Names such as David, Michael, Paul and Robert for boys and Catherine, Elizabeth and Jane for girls remain popular for many years. Others, e.g. Darrell, Darren, Wayne, Chloe, Jade and Zara, are fashionable for only a short period. Names such as Albert, Herbert, Wilfrid, Doris, Gladys and Joyce are now out of fashion and are found mainly among older people. Some older names come back into fashion and there are now many young women called Amy, Emma, Harriet, Laura and Sophie. The birth announcements columns in newspapers give an indication of the names which are currently popular. In Britain these have included Jack, Joshua and Thomas for boys and Emily, Ellie and Chloe for girls and in the US Jacob, Michael and Joshua for boys and Emily, Emma and Madison for girls
People from Wales, Scotland or Ireland, or those who have a cultural background from outside Britain, may choose from an additional set of names. In the US Jews, African Americans or people of Latin American origin may also choose different names.
Example Bank:
• All the men in the family have the same middle name.
• Have you got a middle name?
Cambridge Advanced Learner's Dictionary
middle name
middle name noun [C]
the name some people have between their first name and their last name
Collins Advanced Learner’s English Dictionary
middle name
middle names
1) N-COUNT: usu poss N Your middle name is the name that comes between your first name and your surname.
His middle name is Justin.
2) N-COUNT: usu poss N You can use middle name in expressions such as `discretion was her middle name' and `his middle name is loyalty' to indicate that someone always behaves with a great deal of a particular quality. [HUMOROUS]
Geniality is my middle name. I rarely write a fierce word about any restaurant.