| birefringent | (adj) relating to or characterized by double refraction |
| biretta | (n) a stiff cap with ridges across the crown; worn by Roman Catholic clergy, Syn. berretta, birretta |
| Birectangular | a. [ Pref. bi- + rectangular. ] Containing or having two right angles; |
| Bireme | n. [ L. biremis; bis twice + remus oar: cf. F. birème. ] An ancient galley or vessel with two banks or tiers of oars. [ 1913 Webster ] |
| Biretta | n. Same as Berretta. [ 1913 Webster ] |