three-cornered
adjective /ˌθriː ˈkɔːnəd/
  /ˌθriː ˈkɔːrnərd/
[usually before noun]- having three corners三角形的;有三个角的;三隅的 - a three-cornered hat三角帽 
 
- a three-cornered hat
- involving three people or groups有三人参加的;有三个组的 - a three-cornered contest三方竞争 
 
- a three-cornered contest