Noun

(en noun)

(countable) The act of uniting or joining two or more things into one.

(uncountable) The state of being united or joined.

(countable) That which is united, or made one; something formed by a combination or coalition of parts or members; a confederation; a consolidated body; a league.

(countable) A trade union; a workers' union.

* , chapter=22

, title= The Mirror and the Lamp , passage=In the autumn there was a row at some cement works about the unskilled labour men. A union had just been started for them and all but a few joined. One of these blacklegs was laid for by a picket and knocked out of time.}}

(countable) A joint or other connection uniting parts of machinery, such as pipes.

(countable, set theory) The set containing all of the elements of two or more sets.

(countable) The act or state of marriage.

(uncountable, archaic, euphemistic) Sexual intercourse.

(countable, computing) A data structure that can store any of various items, but only one at a time.

A large, high-quality pearl.

*, II.3.3:

Nonius the senator hath a purple coat as stiff with jewels as his mind is full of vices; rings on his fingers worth 20,000 sesterces, andan union in his ear worth an hundred pounds' weight of gold […].

Noun

(en noun)

a member of a confederacy

an accomplice in a plot

* Macaulay

He found some of his confederates in gaol.

(psychology) An actor who participates in a psychological experiment pretending to be a subject but in actuality working for the researcher (also known as a "stooge").