three-cornered 
adjective
1Triangular: three-cornered hat...
- In the original historic area, authentic shopfronts tempt visitors inside to buy three-cornered hats and bonnets, quills and ink, block-printed stationery and sealing wax, candles, soaps, hams, jams, brass and pewter.
- A group of well-dressed men and women - the men in three-cornered hats, the women in long dresses - are promenading conspicuously beside the river.
- He's usually the one in three-cornered hat when he does his regular turn in period dramas on TV and the big screen.
1.1(Especially of a contest) between three people or groups: a three-cornered fight...
- It is time to employ this legacy in the polarised republican debate to overturn the presumptions that have created a three-cornered contest between monarchists, minimalist republicans and direct-election advocates.
- In April, the Liberal and National parties reached an agreement to end three-cornered contests, but the Liberal Party executive will decide whether to run candidates in the seats of Clarence and Tweed at a meeting on June 21.
- As a result, a three-cornered contest ensued with the former ruling party, the internal opposition and the RPF jockeying for position in a ‘broad-based transitional government’.