adj. Could be someone's having a spasmgasm.
Real citation: "ok...i ask that you PLEASE remove the dancing girl. she creeps me out with her gyrationish bod"
(Mystery girl, Dec. 10, 2006, http://profile.myspace.com/index.cfm?fuseaction=user.viewprofile&friendid=12988756)
Made-up citation: "The gyrationish writhings of my puppy when he's playing are a reminder to buy crack-free dog food."