n. pl. tri·os
a. A composition for three voices or three instruments.
b. A group of three singers or three instrumentalists.
c. The middle, contrasting section of a minuet, scherzo, march, or various other forms.
2. A group of three.
3. A term used for a situation where a person has sexual intercourse with a set of three friends. For example, a boy who has sex with a group of three friends is said to have 'completed the trio'
"Really? Does that mean......"
"Yeah, because he rooted Jenny,Zoe and now Hannah, he's completed the trio."
"He'll definitely have the bad aids now then"