swinging

Etymology 1

The sexual practice is so called after the custom in swing dancing of changing partners after each dance, unlike traditional ballroom dance styles where one has a single partner.

noun

1. The act or motion of that which swings.
   Mr. Henderson's chief trouble seems to be that he cannot forget his old shiftiness of views and his pendulum-like swingings between Liberalism and Independent Labourism[…] 1973, Socialist Review, volume 8, page 331
2. An activity where couples engage in sexual activity with different partners, often in a group setting.

verb

1. present participle and gerund of swing

adj

1. (informal) Fine, good, successful.
   1964, Lou Sullivan, personal diary, quoted in 2019, Ellis Martin, Zach Ozma (editors), We Both Laughed In Pleasure Didn't do anything great except saw "The Beatles" on The Ed Sullivan Show and Kathy practically had a bird. They are sorta cute but I think Ringo is swingin, George is cute, Paul is a good singer and John is icky. Too!
   The party was swinging.
2. Sexually promiscuous.
   Hey, everyone fantasizes about what kind of swinging stud or studette they could be if they were only free from the shackles of domesticity. February 23, 2003, Bob Goldman, “Welcome To Splitsville”, in Florida Today

Etymology 2

adj

1. Alternative form of swingeing