Definition of unions:
(n) :
(countable) The act of uniting or joining two or more things into one.
(n) :
(uncountable) The state of being united or joined; a state of unity or harmony.
(n) :
(countable) Something united, or made one; something formed by a combination or coalition of parts or members; a confederation; a consolidated body; a league.
(n) :
(countable) A trade union; a workers' union.
(n) :
(countable) An association of students at a university for social and/or political purposes; also in some cases a debating body.
(n) :
(countable) A joint or other connection uniting parts of machinery, such as pipes.